cmake/submodules: notify user about gitconfig for automatic update

Co-Authored-By: grooverdan <daniel@linux.ibm.com>

Most of the mtr tests in the galera_3nodes suite fail
for a variety of reasons with a variety of errors.

This patch fixes several substantial flaws
in the galera_3nodes suite tests and in the mtr framework
service files, adapting the tests from galera_3nodes
for the current version of MariaDB.

This patch also synchronizes some galera_3nodes-related
files with the latest changes made for MDEV-17835 (v2 patch)
and for MDEV-18379 in other branches (10.2 and 10.3).

Closes #1161

The code path where the table was not being rebuilt during ALTER TABLE
was not covered by the test. Add coverage, and remove the debug assertion
that could fail in this case.

Followup for db8f0dae

and in fef9013d

fixes memory leaks in restart_mysqld.inc tests

Followup for 8f5ea83f

MDEV-18426: Most of the mtr tests in the galera_3nodes suite fail

Most of the mtr tests in the galera_3nodes suite fail
for a variety of reasons with a variety of errors.
Some tests simply need to add the missing "connection"
lines to the result files, but many of them fail due
to substantial errors that require reworking test files.

This patch adds the missing "connection" lines to
the result files and fixes several substantial flaws
in the galera_3nodes suite tests and in the mtr framework
service files, adapting the tests from galera_3nodes
for the current version of MariaDB.

https://jira.mariadb.org/browse/MDEV-18426

i_s_innodb_mutexes_fill_table(): Use the C++ RAII pattern
to ensure that the mutexes are released if an OK()
macro returns from the function prematurely.

An uninitialized buffer is passed to row_sel_store_mysql_rec() but
InnoDB may not initialize everything. Looks like it's ok in most cases
but not always.
The partially initialized buffer was later passed to
ha_innobase::write_row() which reads random NULL bit values for
virtual columns and random stuff happens.

No test case for MariaDB 10.2 was found.
The test case for MariaDB 10.3 involves partitioning,
system versioning and the TRASH_ALLOC fill pattern 0xA5.
Test case depends very much on the number and layout of columns.
Think about 0xA5 byte for a NULL bit mask.

row_sel_store_mysql_rec(): always initialize virtual columns NULL bit

Closes #1144

The list of table constraints doesn't include foreign keys and uniques.
So we replace DROP CONSTRAINT with DROP [FOREIGN] KEY in this case.

MDEV-16905 ASAN heap-use-after-free in __interceptor_strnlen / ... / TABLE::verify_constraints upon INSERT into temporary table with CHECK constraint

just a test case

MDEV-18239 ASAN use-after-poison in process_str_arg / ... / mark_unsupported_func or unexpected ER_BAD_FIELD_ERROR upon ALTER TABLE

renaming columns in a CHECK constraint during ALTER TABLE
taints the original TABLE and requires m_need_reopen=1.

In this case, though, renaming was redundant, so just don't do it.

CONNECT used to compute table file path as
table->s->db_name + table->s->table_name
instead of using table->s->path. This was incorrect and now it breaks
for temporary tables during ALTER TABLE.

Temporarily "fix" it by making CONNECT to use what it always used
as a table name - the last component in the table->s->path.

no longer needed

MDEV-18083 ASAN heap-use-after-free in Field::set_warning_truncated_wrong_value upon inserting into temporary table

remove TABLE_SHARE::error_table_name() and TABLE_SHARE::orig_table_name
(that was allocated in a wrong memroot in this bug).

instead, simply set TABLE_SHARE::table_name correctly.

remove thd->find_temporary_table()

Temporarily disable a test for
commit 2175bfce
because fixing it in 10.2 requires updating libmariadb.

buf_page_is_corrupted(): Read the global variable srv_checksum_algorithm
only once in order to avoid a race condition when
SET GLOBAL innodb_checksum_algorithm=...;
is being executed concurrently with this function.

  FOREIGN DATA WRAPPER to work with CONNECT engine
  modified:   storage/connect/tabjdbc.cpp

- Add a function to retrieve User variable value (DEVELOPMENT only)
  modified:   storage/connect/ha_connect.cc
  modified:   storage/connect/jsonudf.cpp
  modified:   storage/connect/jsonudf.h
  modified:   storage/connect/tabjdbc.cpp

Store original charset during client authentication, and restore it for
COM_RESET_CONNECTION

This is joint work with Oleksandr Byelkin.