MDEV-17835: Remove wsrep-sst-method=xtrabackup

The second line of changes related to replacing xtrabackup with
mariabackup:

1) All unnecessary references to xtrabackup are removed from
the documentation, from some comments, from the control files
that are used to prepare the packages.

2) Made corrections of the tests from the galera_3nodes suite
that mentioned xtrabackup or the old (associated with xtrabackup)
version of innobackupex.

3) Fixed flaws in the galera_3nodes mtr suite control scripts,
because of which they could not work with mariabackup.

4) Fixed numerous bugs in the SST scripts and in the mtr test
files (galera_3nodes mtr suite) that prevented the use of Galera
with IPv6 addresses.

5) Fixed flaws in tests for rsync and mysqldump (for galera_3nodes
mtr tests suite). These tests were not performed successfully without
these fixes.

https://jira.mariadb.org/browse/MDEV-17835

MDEV-11369 (instant ADD COLUMN) introduced a regression in the case the
leftmost leaf page of the clustered index is empty except for the
hidden metadata record.

btr_pcur_store_position(): If the only record in the leftmost leaf page
is the metadata record, store the position before the first user record
in the tree.

InnoDB does not allow creating multiple FULLTEXT INDEX
in ALGORITHM=INPLACE. This constraint was not being properly
enforced after MariaDB started to support ALGORITHM=INSTANT
and instant ADD COLUMN.

As a side effect of this bug, we again allow ALGORITHM=INPLACE
to rebuild a table when one FULLTEXT INDEX survives.
Also, we are returning a more accurate reason for refusing LOCK=NONE.

innobase_fulltext_exist(): Return the number of fulltext indexes.

ha_innobase::check_if_supported_inplace_alter(): If the table
needs to be rebuilt, refuse the operation if multiple fulltext
indexes would remain.

This assertion would fail when a secondary index record for an
instantly added column was accessed.

It is unclear to me why this code path is executed so rarely.
I was unable to cover it even when using FORCE INDEX.

row_sel_sec_rec_is_for_clust_rec(): Remove the assertion, and use
the proper function rec_get_nth_cfield().

row_sel_store_mysql_field_func(): Simply use rec_get_nth_cfield()
instead of duplicating its logic.

row_drop_table_for_mysql(): Fix a regression introduced in MDEV-16515.
Similar to the follow-up fixes MDEV-16647 and MDEV-17470, we must make
the internal tables of FULLTEXT INDEX immune to kills, to avoid noise
and resource leakage on DROP TABLE or ALTER TABLE. (Orphan internal tables
would be dropped at the next InnoDB startup only.)

server shutdown.

Prior to adding current thd to the global thd list, initialize
thd->mysys_var->current_cond / thd->mysys_var->current_mutex.

Otherwise thd_destructor_proxy can miss the abort condition, which is set
by the shutdown thread.

Problem:
========
MLOG_FILE_WRITE_CRYPT_DATA redo log fails to apply type for
the crypt_data present in the space. While processing the double-write
buffer pages, page fails to decrypt. It leads to warning message.

Fix:
====
Set the type while parsing MLOG_FILE_WRITE_CRYPT_DATA redo log.
If type and length is of invalid type then mark it as corrupted.

Corrects 94d722b6

- There is no need to wait for crypt thread to stop accessing space while
dropping the garbage encrypted tablespace during recover.

Allow table definition cache be bigger than open table cache (due to problem with VIEWs and prepared statements).

Implement according to standard SQL specification 2008.
The check_constraints table is used for fetching metadata about
the constraints defined for tables in all databases.

There were some result files which failed after running mtr.
These files are updated with newly create record with mtr --record.

This might apply to 10.1 and 10.2 as well, but I cannot run that test
there without installing third-party software. The test would expect
"innobackupex" to be in path. If I add a wrapper script that invokes
mariabackup --innobackupex, then on 10.2 the cluster would fail to start
up due to a version number mismatch.

Poisoning memory after munmap() and friends is totally incorrect as this memory
could be anything.

os_mem_free_large(): remove memory poisoning

If galera.galera_gtid_slave_sst_rsync is repeated more than once it will fail due incorrect GTID position. After stopping SLAVE node reset also GTID_SLAVE_POS variable.

The merge commit d833bb65 did not
correctly merge the commit 03eb1593.

Closes #948

This mutex can be freed when server shuts down (when thread_count goes down to 0)
, but it is still used inside THD::~THD() when Statement_map is destroyed.

The fix is to call Statement_map::reset() at the point where thread_count
is still positive, and avoid locking LOCK_prepared_stmt_count in THD
destructor.

Add the test case. The actual bug was fixed in MDEV-17541.

Closes #811

When performing a hash search via HASH_SEARCH we first look at a key of a node
and then at its pointer to the next node in chain. If we have those in one cache
line instead of a two we reduce memory reads.

I found dict_table_t, fil_space_t and buf_page_t suitable for such improvement.

This was introduced in 1a7a0189
MDEV-16557 Remove INNOBASE_SHARE::idx_trans_tbl

ha_innobase::innobase_get_index: remove incorrect assertion.
Index nullability is checked in subsequent ifs.

Closes #1079

The fil_system_t::name_hash was removed already earlier,
in commit 05863142.
The fil_space_t::name_hash was thus made an orphan data field.

MDEV-16499 ER_NO_SUCH_TABLE_IN_ENGINE followed by "Please drop the table and recreate" upon adding FULLTEXT key to table with virtual column

log_group_file_header_flush(): Use a stack-local variable
instead of the heap-allocated buffers.

Closes #1060