As part of the SPATIAL INDEX implementation in InnoDB,
dict_index_t was expanded by a rtr_ssn_t field. There are only
3 operations for this field, all protected by rtr_ssn_t::mutex:

* btr_cur_search_to_nth_level() stores the least significant 32 bits
of the 64-bit value that is stored in the index root page.
(This would better be done when the table is opened for the
very first time.)
* rtr_get_new_ssn_id() increments the value by 1.
* rtr_get_current_ssn_id() reads the current value.

All these operations can be implemented equally safely by using
atomic memory access operations.

correct the help text

When we move data we should fix buffer string length

Enable tests with additional galera output to find out actual
reason for test failures.

under LOCK TABLES we still have to open everything, otherwise DML
prelocking will try to take an MDL on a table that wasn't in the
LOCK TABLES list.

MDEV-21421 : Galera test sporadic failure on galera.galera_as_slave_gtid_myisam: Result length mismatch

Add wait_condition so that drop table has time to replicate to
Galera cluster.

The test was incompatible with ./mtr --repeat=2 until
commit 2d6719d7
fixed that.

It turns out that the failing assertion that we disabled in
commit 3db94d24
is bogus and can fail when the change buffer is emptied
during the last batch of crash recovery. The reason for this
is the condition around the page_create_empty() call in
page_cur_delete_rec(). The condition was removed in MariaDB
Server 10.5 as part of MDEV-12353, in
commit 7ae21b18 and
commit f8a9f906.

The bug that the assertion aimed to catch is MDEV-22497, which
was fixed in commit 26aab96e.

only MDL-prelock but do not open FK child tables for read-only (RESTRICT)
FK actions.

Tables still needs to be opened for CASCADE actions, see 9180e866

MDEV-21515 : Galera test sporadic failure on galera.galera_wsrep_new_cluster: Result content mismatch

Test starts two servers and we do not know order they really start,
thus wsrep_local_index can be 1 or 2.

Test seems to work.

We must ensure that the NUL will not terminate the query string.

Replace the 30-second sleep in the test with proper
DEBUG_SYNC interlocking.

MDEV-21437 MariaDB's SUSE/SLES packages don't "provide" all of the same capabilities as the platform's default packages

Fixing a race condition while collecting the engine independent statistics.

Thread1>
1) start running "ANALYZE TABLE t PERISTENT FOR COLUMNS (..) INDEXES ($list)"
2) Walk through $list and save it in TABLE::keys_in_use_for_query
3) Close/re-open tables

Thread2>
1) Make some use of table t. This involves taking table t from
   the table cache, and putting it back (with TABLE::keys_in_use_for_query reset to 0)

Thread1>
continue collecting EITS stats. Since TABLE::keys_in_use_for_query is set to 0 we
will not collect statistics for indexes in $list.

commit 6495806e removed all reads
of buf_page_t::write_size. Let us remove the field altogether.

commit d467bb7e accidentally
broke the build without WSREP, by misplacing an #endif.

This is a partial backport of
commit 5e7e7153 from 10.4.

assert_trx_is_free(): Assert !is_wsrep().

trx_init(): Do not initialize trx->wsrep, because it must have been
initialized already.

trx_commit_in_memory(): Invoke wsrep_commit_ordered(). This call
was being skipped, because the transaction object had already been
freed to the pool.

trx_rollback_for_mysql(), innobase_commit_low(),
innobase_rollback_trx(): Always reset trx->wsrep.

		FOREIGN_KEY_CHECKS is disabled

- Referenced index can be null While renaming the referenced column name.
In that case, rename the referenced column name in dict_foreign_t and
find the equivalent referenced index.

queues.c cleanup and refactoring.

Restore old version of _downhead() (from before cd483c55)
that works well in an average case. Use it for queue_fix().

Move existing specialized version of _downhead() to queue_replace()
where it'll be handling the case it was specifically optimized for
(moving the element to the end of the queue).
And correct it to fix the heap not only down, but also up
(this fixes BUG#30301356).

Add unit tests.

Collateral cosmetic fixes.