Initial support for sql standard <explicit table> expressions
The <explicit table>
    TABLE <table or query name>
    is equivalent to the <query specification>
    SELECT * FROM <table or query name>
Deal with the conflict caused by ANALYZE TABLE t1; being both
a request for table statistics and analyzing an SQL statement.

This test case exposed 2 different bugs:
- When replacing a range with an index scan on a covering key
  in test_if_skip_sort_order() we didn't disable filtering.
  Filtering does not make much sense in this case.
  - Fixed by disabling filtering in this case.
- Range_rowid_filter::fill() did not take into account that keyread
  could already active, which caused an assert when it tried to
  activate another keyread.
  - Fixed by remembering old keyread state at start and restoring it
    at end.

Other things:
- ha_start_keyread() allowed multiple calls. This is wrong, especially
  as we do no check if the index changed!
  I added an assert() to ensure that we don't call it there is already
  an active keyread.
- ha_end_keyread() always called ha_extra(), even if keyread was not
  active.  Added a check to avoid the extra call.

This patch also fixes
MDEV-31391 Assertion `((best.records_out) == 0.0 ... failed

Cost changes caused by this change:
- range queries with join buffer now have a notable smaller cost.
- range ranges are bit more expensive as the MULTI_RANGE_COST is now
  properly applied to it in all cases (this extra cost is equal to a
  key lookup).
- table scan cost is slight smaller as we now assume data is cached in
  the engine after the first scan pass. (We did this before for range
  scans and other access methods).
- partition tables had wrong values for max_row_blocks and
  max_index_blocks.  Correcting this, causes range access on
  partitioned tables to have slightly higher cost because of the
  increased estimated IO.
- Using first match + join buffer caused 'filtered' to be calcualted
  wrong.  (Only affected EXPLAIN, not query costs).
- Added cost_without_join_buffer to optimizer_trace.
- check_quick_select() adjusted the number of rows according to persistent
  statistics, but did not adjust cost. Now fixed.

The big change in the patch are:

- In best_access_path(), where we now are using storing the cost in
  'ALL_READ_COST cost' and only converting it to a double at the end.
   This allows us to more exactly calculate the effect of the join_cache.
- In JOIN_TAB::estimate_scan_time(), store the cost also in a
  ALL_READ_COST object.

One of effect if this change is that when joining very small tables:

t1    some_access_method
t2    range
t3    ALL         Use join buffer

This is swiched to

t1      some_access_method
t3      ALL
t2      range      use join buffer

Both plans has the same cost, but as table scan in this case has less
cost than rang, the table scan will be considered first and thus have
precidence.

Test case changes:
- optimizer_trace          - Addition of cost_without_join_buffer
- subselect_mat_cost_bugs  - Small tables and scan versus range
- range & range_mrr_icp    - Range + join_cache is faster than ref
- optimizer_trace          - cost_without_join_buffer, smaller scan cost,
                             range setup cost.
- mrr                      - range+join_buffer used as smaller cost

This is 11.0 part of the fix: in 11.0, get_costs_for_tables() calls
best_access_path() for all possible tables, for each call it saves
a POSITION object with the access method and "loose_scan_pos"
POSITION object.
The latter is saved even if there is no possible LooseScan plan. Saving
is done by copying POSITION objects which may generate a spurious
UBSan error.

The problem was a wrong assert. I changed it to match the code in
best_access_path().

The given test case was a bit tricky for the optimizer, which first
decided on using a index scan (because of force index), but then
test_if_skip_sort_order() decided to use range anyway to handle
distinct.

Problem was an overflow when calculating number of join cache refills.

This was caused of two minor issues:
- get_quick_record_count() returned the number of rows for range with
  least cost, when it should have returned the minum number of rows
  for any range.
- When changing REF to RANGE, we also changed records_out, which
  should not be done (number of records in the result will not
  change).

The above change can cause a small change in row estimates where the
optimizer chooses a clustered key with more rows than a range one
secondary key (unlikely case).

In Loose_scan_opt::save_to_position, initialize
POSITION::firstmatch_with_join_buf.

The code in create_internal_tmp_table() didn't take into account that
now temporary (derived) tables may have multiple indexes:

- one index due to duplicate removal
   = In this example created by conversion of big-IN(...) into subquery
   = this index might be converted into a "unique constraint" if the key
     length is too large.
- one index added by derived_with_keys optimization.

Make create_internal_tmp_table() handle multiple indexes.

Before this patch, use of a unique constraint was indicated in
TABLE_SHARE::uniques. This was ok as unique constraint was the only index
in the table. Now it's no longer the case so TABLE_SHARE::uniques is removed
and replaced with an in-memory-only flag HA_UNIQUE_HASH.

This patch is based on Monty's patch.
Co-Author: Monty <monty@mariadb.org>

This makes it easier to run test on just events.

This makes it easier to run test on just the MRG_MYISAM engine.

Other things:
- Renamed merge-big.test to flush_corruption.test as it does not
  have anything to do with merge tables.

The problem was that for merge tables without any underlaying tables the
block size was 0, which the code could not handle.

Fixed by ensuring that MERGE tables never have a block size of 0.
Fixed also a wrong assumption of number of seeks needed to scan
merge tables.

Introduces @@optimizer_switch flag: hash_join_cardinality

When this option is on, use EITS statistics to produce tighter bounds
for hash join output cardinality.

This patch is an extension / replacement to a similar patch in 10.6

New features:
- optimizer_switch hash_join_cardinality is on by default
- records_out is set to fanout when HASH is used
- Fixed bug in is_eits_usable: The function did not work with views

rtr_ins_enlarge_mbr(): Relax the assertion that was added in
commit f27e9c89
to cover also table-rebuilding DDL. We only need
btr_cur->rtr_info->thr for acquiring R-tree locks,
and the thread that is executing a DDL operation has exclusive
access to the being-built index or the copy of the being-rebuilt table.

Set the lock wait timeout to 1 beforehand, and reset it afterwards, to
avoid lock conflict caused by opening the same table twice in case of
self-reference.

- assign spider->share early when !new_share
- remove locking before spider_share_init_{sts,crd}

Extracted out common subroutines, gave more meaningful names etc,
added comments etc.

Also:
- Documented active servers load balancing reads, and other fields in
  SPIDER_SHARE etc.
- Removed commented out code
- Documented and refactored self-reference check
- Removed some unnecessary functions
- Renamed unhelpful roop_count
- Refactored spider_get_{sts,crd}, where we turn get_type into an enum
- Cleaned up spider_mbase_handler::show_table_status() and
  spider_mbase_handler::show_index()

Deb-autobakes where failing with:

dh_missing: warning: usr/share/mysql/mysql-test/mysql-test-run exists in debian/tmp but is not installed to anywhere
dh_missing: warning: usr/share/mysql/mysql-test/mtr exists in debian/tmp but is not installed to anywhere
dh_missing: warning: usr/share/mysql/mysql-test/mariadb-test-run exists in debian/tmp but is not installed to anywhere
dh_missing: warning: usr/share/mysql/mysql-test/mysql-test-run.pl exists in debian/tmp but is not installed to anywhere

Add all to mariadb-test.install and remove mariadb-test.links

Applying b98375f9 instead of 9b32e4b1 for version 10.5-10.8.
Applying 5075f4e0 instead of 9b32e4b1 for version 10.9+.

AWK is used in autobake-debs.sh for printing information
about created DEB packages.

This can be rewrite with bash inner commands read and echo.

AWK in used in Debian SysV-init and postinst scripts to determine
is there enough space starting MariaDB database or create new
database to target destination.

These AWK scripts can be rewrited to use pure SH or help
using Coreutils which is mandatory for usage of MariaDB currently.

Reasoning behind this is to get rid of one very less used dependency

Extend the portability of ANALYZE FORMAT=JSON by using the microsecond
timer if cycles isn't available.

Reviewer: Sergei Petrunia <sergey@mariadb.com>

make the compile-time logic in my_timer_cycles() also #define
MY_TIMER_ROUTINE_CYCLES to indicate which implementation it is using.
Then, make my_timer_init() use MY_TIMER_ROUTINE_CYCLES.

This leaves us with just one set of compile-time #if's which determine
how we read time in #cycles.

Reviewer (and commit message author): Sergei Petrunia <sergey@mariadb.com>

This fixes up commit e3f6e1c9