if the server is started with --ssl but without neither --ssl-key nor
--ssl-cert, let it automatically generate a self-signed certificate.
It's generated in memory only and never saved to disk.

when neither --ssl-key nor --ssl-cert were set, the errror
was "Private key does not match the certificate public key"

changed to "Unable to get certificate"

verify that --ssl-verify-server-cert detects cert mismatch,
but with --disable-ssl-verify-server-cert the connection succeeds

implement --ssl-fp and --ssl-fplist for all clients.
--ssl-fp takes one certificate fingerprint, for example,
00:11:22:33:44:55:66:77:88:99:AA:BB:CC:DD:EE:FF:00:11:22:33

--ssl-fplist takes a path to a file with one fingerprint per line.

if the server's certificate fingerprint matches ssl-fp or is found
in the file - the certificate is considered verified.
If the fingerprint is specified but doesn't match - the connection
is aborted independently from the --ssl-verify-server-cert

if the client enabled --ssl-verify-server-cert, then
the server certificate is verified as follows:

* if --ssl-ca or --ssl-capath were specified, the cert must have
  a proper signature by the specified CA (or CA in the path)
  and the cert's hostname must match the server's hostname.
  If the cert isn't signed or a hostname is wrong - the
  connection is aborted.

* if MARIADB_OPT_TLS_PEER_FP was used and the fingerprint matches,
  the connection is allowed, if it doesn't match - aborted.

* If the connection uses unix socket or named pipes - it's allowed.
  (consistent with server's --require-secure-transport behavior)

otherwise the cert is still in doubt, we don't know if we can trust
it or there's an active MitM in progress.

* If the user has provided no password or the server requested an
  authentication plugin that sends the password in cleartext -
  the connection is aborted.

* Perform the authentication. If the server accepts the password,
  it'll send SHA2(scramble || password hash || cert fingerprint)
  with the OK packet.

* Verify the SHA2 digest, if it matches - the connection is allowed,
  otherwise it's aborted.

char is a character, uchar is an octet.
casts removed (or added) as needed

not default_mysqld.cnf. The latter has only server settings,
it misses mtr-specific client configuration

Except for spider, that doesn't use mysqld.1 server
and default_my.cnf starts it automatically.
Spider tests have to include both default_mysqld.cnf and
default_client.cnf

it's for client auth plugins only, server auth plugin should never
return it, because they cannot send a correct OK packet.
(OK packet is quite complex and carries a lot of information that
only the server knows)

as suggested by Monty

This commit addresses multiple server shutdown problems observed on macOS,
Solaris, and FreeBSD:

1. Corrected a non-portable assumption where socket shutdown was expected
to wake up poll() with listening sockets in the main thread.

Use more robust self-pipe to wake up poll() by writing to the pipe's write
end.

2. Fixed a random crash on macOS from pthread_kill(signal_handler)
when the signal_handler was detached and the thread had already exited.

Use more robust `kill(getpid(), SIGTERM)` to wake up the signal handler
thread.

3. Made sure, that signal handler thread always exits once `abort_loop` is
set, and also calls `my_thread_end()` and clears `signal_thread_in_use`
when exiting.

This fixes warning "1 thread did not exit"  by `my_global_thread_end()`
seen on FreeBSD/macOS when the process is terminated via signal.

Additionally, the shutdown code underwent light refactoring
for better readability and maintainability:
- Modified `break_connect_loop()` to no longer wait for the main thread,
  aligning behavior with Windows (since 10.4).
- Removed dead code related to the unused `USE_ONE_SIGNAL_HAND`
  preprocessor constant.
- Eliminated support for `#ifndef HAVE_POLL` in `handle_connection_sockets`
  This code is also dead, since 10.4

This is done for symmetry with mariadb-dump, which does not use threads
but allows parallelism via --parallel

Traditional --use-threads can still be used, it is synonymous
with --parallel

-  --parallel=N with or without --single-transaction
-  Error cases (too many connections, emulate error on one connection)
-  Windows specific test for named pipe connections

At the moment, it only works with --tab, to execute "SELECT INTO OUTFILE"
queries concurrently.

Uses connection_pool for concurrent execution.

Parallelism is achieved by using mysql_send_query on multiple connections
without waiting for results, and using IO multiplexing (poll/IOCP) to
wait for completions.

Refresh libmariadb to pick up CONC-676 (fixes for IOCP use with named pipe)

- make connect_to_db() return MYSQL*, we'll reuse the function for
  connection pool.

- Remove variable 'mysql_connection', duplicated by variable 'mysql'
- do not attempt to start slave if connection did not succeed,#
  and fix mysqldump.result

Improve the performance of slave connect using B+-Tree indexes on each binlog
file. The index allows fast lookup of a GTID position to the corresponding
offset in the binlog file, as well as lookup of a position to find the
corresponding GTID position.

This eliminates a costly sequential scan of the starting binlog file
to find the GTID starting position when a slave connects. This is
especially costly if the binlog file is not cached in memory (IO
cost), or if it is encrypted or a lot of slaves connect simultaneously
(CPU cost).

The size of the index files is generally less than 1% of the binlog data, so
not expected to be an issue.

Most of the work writing the index is done as a background task, in
the binlog background thread. This minimises the performance impact on
transaction commit. A simple global mutex is used to protect index
reads and (background) index writes; this is fine as slave connect is
a relatively infrequent operation.

Here are the user-visible options and status variables. The feature is on by
default and is expected to need no tuning or configuration for most users.

binlog_gtid_index
  On by default. Can be used to disable the indexes for testing purposes.

binlog_gtid_index_page_size (default 4096)
  Page size to use for the binlog GTID index. This is the size of the nodes
  in the B+-tree used internally in the index. A very small page-size (64 is
  the minimum) will be less efficient, but can be used to stress the
  BTree-code during testing.

binlog_gtid_index_span_min (default 65536)
  Control sparseness of the binlog GTID index. If set to N, at most one
  index record will be added for every N bytes of binlog file written.
  This can be used to reduce the number of records in the index, at
  the cost only of having to scan a few more events in the binlog file
  before finding the target position

Two status variables are available to monitor the use of the GTID indexes:

  Binlog_gtid_index_hit
  Binlog_gtid_index_miss

The "hit" status increments for each successful lookup in a GTID index.
The "miss" increments when a lookup is not possible. This indicates that the
index file is missing (eg. binlog written by old server version
without GTID index support), or corrupt.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>

Also deprecating table params not implemented in MDEV-28856.

This patch augments Gtid_log_event with the user thread-id.
In particular that compensates for the loss of this info in
Rows_log_events.

Gtid_log_event::thread_id gets visible in mysqlbinlog output like

  #231025 16:21:45 server id 1  end_log_pos 537 CRC32 0x1cf1d963  GTID 0-1-2 ddl thread_id=10

as 64 bit unsigned integer.

While the size of Gtid event has grown by 8-9 bytes
replication from OLD <-> NEW is not affected by it.

This work was started by the late Sujatha Sivakumar.
Brandon Nesterenko took it over, reviewed initial patches and extended
the work.

Reviewed-by: <andrei.elkin@mariadb.com>

Summary
=======
With FULL_NODUP mode, before image inclues all columns and after
image inclues only the changed columns. flashback will swap the
value of changed columns from after image to before image.
For example:
  BI: c1, c2, c3_old, c4_old
  AI: c3_new, c4_new
flashback will reconstruct the before and after images to
  BI: c1, c2, c3_new, c4_new
  AI: c3_old, c4_old

Implementation
==============
When parsing the before and after image, position and length of
the fields are collected into ai_fields and bi_fields, if it is an
Update_rows_event and the after image doesn't includes all columns.

The changed fields are swapped between bi_fields and ai_fields.
Then it recreates the before image and after image by using
bi_fields and ai_fields. nullbit will be set to 1 if the
field is NULL, otherwise nullbit will be 0.

It also optimized flashback a little bit.
- calc_row_event_length is used instead of print_verbose_one_row
- swap_buff1 and swap_buff2 are removed.

BASE 62 uses 0-9, A-Z and then a-z to give the numbers 0-61. This patch
increases the range of the string functions to cover this.

Based on ideas and tests in PR #2589, but re-written into the charset
functions.

Includes fix by Sergei, UBSAN complained:
ctype-simple.c:683:38: runtime error: negation of -9223372036854775808
cannot be represented in type 'long long int'; cast to an unsigned
type to negate this value to itself
Co-authored-by: Weijun Huang <huangweijun1001@gmail.com>
Co-authored-by: Sergei Golubchik <serg@mariadb.org>

           Field_new_decimal::store_value(const my_decimal*, int*)

Analysis
========
When rpl applier is unpacking a before row image, Field::reset() will be
called before setting a field to null if null bit of the field is set in
the row image. For Field_new_decimal::reset(), it calls
Field_new_decimal::store_value() to reset the value. store_value() asserts
that the field is in the write_set bitmap since it thinks the field is
updating.

But that is not true for the row image generated in FULL_NODUP
mode. In the mode, the before image includes all fields and the after
image includes only updated fields.

Fix
===
In the case unpacking binlog row images, the assertion is meaningless.
So the unpacking field is marked in write_set temporarily to avoid the
assertion failure.

When innodb_undo_log_truncate=ON causes an InnoDB undo tablespace
to be truncated, we must guarantee that the undo tablespace will
be rebuilt atomically: After mtr_t::commit_shrink() has durably
written the mini-transaction that rebuilds the undo tablespace,
we must not write any old pages to the tablespace.

To guarantee this, in trx_purge_truncate_history() we used to
traverse the entire buf_pool.flush_list in order to acquire
exclusive latches on all pages for the undo tablespace that
reside in the buffer pool, so that those pages cannot be written
and will be evicted during mtr_t::commit_shrink(). But, this
traversal may interfere with the page writing activity of
buf_flush_page_cleaner(). It would be better to lazily discard
the old pages of the truncated undo tablespace.

fil_space_t::is_being_truncated, fil_space_t::clear_stopping(): Remove.

fil_space_t::create_lsn: A new field, identifying the LSN of the
latest rebuild of a tablespace.

buf_page_t::flush(), buf_flush_try_neighbors(): Evict pages whose
FIL_PAGE_LSN is below fil_space_t::create_lsn.

mtr_t::commit_shrink(): Update fil_space_t::create_lsn and
fil_space_t::size right before the log is durably written and the
tablespace file is being truncated.

fsp_page_create(), trx_purge_truncate_history(): Simplify the logic.

Reviewed by: Thirunarayanan Balathandayuthapani, Vladislav Lesin
Performance tested by: Axel Schwenke
Correctness tested by: Matthias Leich

trx_purge_free_segment(), trx_purge_truncate_rseg_history():
Do not claim that the blocks will be modified in the mini-transaction,
because that will not always be the case. Whenever there is a
modification, mtr_t::set_modified() will flag it.

The debug assertion that failed in recovery is checking that all
changes to data pages are covered by log records. Due to these
incorrect calls, we would unnecessarily write unmodified data pages,
which is something that commit 05fa4558
aims to avoid.

The incorrect calls had originally been added in
commit de31ca6a (MDEV-32820) and
commit 86767bcc (MDEV-29593).

Reviewed by: Vladislav Lesin
Tested by: Elena Stepanova

perfschema thread walker needs to take thread's LOCK_thd_kill to prevent
the thread from disappearing why it's being looked at.
But there's no need to lock it for the current thread.

In fact, it was harmful as some code down the stack might take
LOCK_thd_kill (e.g. set_killed() does it, and my_malloc_size_cb_func()
calls set_killed()). And it caused a bunch of mutexes being locked under
LOCK_thd_kill, which created problems later when my_malloc_size_cb_func()
called set_killed() at some unspecified point under some
random mutexes.

same assertion with spider. spider status variables
didn't expect to be queried from a different thread
without LOCK_thd_data.

And they didn't expect to be queried under LOCK_thd_data either
(because spider_get_trx() calls thd_set_ha_data()).

reduce code duplication