release MDL on the trigger as early as possible, after everything that
cannot be done concurrently was done (under MDL), but before relocking
tables.

The reason was that WSREP code in mysql_create_or_drop_trigge() did
jump to an exit label that did not do proper cleanup of state.
Fixed by ensuring that also WSREP code goes trough the cleanup process.

The problem was that in a timeout event,
thd->lex->restore_backup_query_tables_list() was called when it should
not have been.

Patch tested with the script in MDEV-25651 (not suitable for mtr)

The bug is that we don't have a a lock on the trigger name, so it is
possible for two threads to try to create the same trigger at the same
time and both thinks that they have succeed.
Same thing can happen with drop trigger or a combinations of create and
drop trigger.

Fixed by adding a mdl lock for the trigger name for the duration of the
create/drop.

Patch tested by Elena

- Indentation changes
- Fixed wrong name for used in DBUG_ENTER
- Added some code comments

MDEV-22829 SIGSEGV in _ma_reset_history on LOCK

The used code is largely based on code from Tencent

The problem is that in some rare cases there may be a conflict between .frm
files and the files in the storage engine. In this case the DROP TABLE
was not able to properly drop the table.

Some MariaDB/MySQL forks has solved this by adding a FORCE option to
DROP TABLE. After some discussion among MariaDB developers, we concluded
that users expects that DROP TABLE should always work, even if the
table would not be consistent. There should not be a need to use a
separate keyword to ensure that the table is really deleted.

The used solution is:
- If a .frm table doesn't exists, try dropping the table from all storage
  engines.
- If the .frm table exists but the table does not exist in the engine
  try dropping the table from all storage engines.
- Update storage engines using many table files (.CVS, MyISAM, Aria) to
  succeed with the drop even if some of the files are missing.
- Add HTON_AUTOMATIC_DELETE_TABLE to handlerton's where delete_table()
  is not needed and always succeed. This is used by ha_delete_table_force()
  to know which handlers to ignore when trying to drop a table without
  a .frm file.

The disadvantage of this solution is that a DROP TABLE on a non existing
table will be a bit slower as we have to ask all active storage engines
if they know anything about the table.

Other things:
- Added a new flag MY_IGNORE_ENOENT to my_delete() to not give an error
  if the file doesn't exist. This simplifies some of the code.
- Don't clear thd->error in ha_delete_table() if there was an active
  error. This is a bug fix.
- handler::delete_table() will not abort if first file doesn't exists.
  This is bug fix to handle the case when a drop table was aborted in
  the middle.
- Cleaned up mysql_rm_table_no_locks() to ensure that if_exists uses
  same code path as when it's not used.
- Use non_existing_Table_error() to detect if table didn't exists.
  Old code used different errors tests in different position.
- Table_triggers_list::drop_all_triggers() now drops trigger file if
  it can't be parsed instead of leaving it hanging around (bug fix)
- InnoDB doesn't anymore print error about .frm file out of sync with
  InnoDB directory if .frm file does not exists. This change was required
  to be able to try to drop an InnoDB file when .frm doesn't exists.
- Fixed bug in mi_delete_table() where the .MYD file would not be dropped
  if the .MYI file didn't exists.
- Fixed memory leak in Mroonga when deleting non existing table
- Fixed memory leak in Connect when deleting non existing table

Bugs fixed introduced by the original version of this commit:
MDEV-22826 Presence of Spider prevents tables from being force-deleted from
           other engines

MDEV-22531 Remove maria::implicit_commit()
MDEV-22607 Assertion `ha_info->ht() != binlog_hton' failed in
           MYSQL_BIN_LOG::unlog_xa_prepare

From the handler point of view, Aria now looks like a transactional
engine. One effect of this is that we don't need to call
maria::implicit_commit() anymore.

This change also forces the server to call trans_commit_stmt() after doing
any read or writes to system tables.  This work will also make it easier
to later allow users to have system tables in other engines than Aria.

To handle the case that Aria doesn't support rollback, a new
handlerton flag, HTON_NO_ROLLBACK, was added to engines that has
transactions without rollback (for the moment only binlog and Aria).

Other things
- Moved freeing of MARIA_SHARE to a separate function as the MARIA_SHARE
  can be still part of a transaction even if the table has closed.
- Changed Aria checkpoint to use the new MARIA_SHARE free function. This
  fixes a possible memory leak when using S3 tables
- Changed testing of binlog_hton to instead test for HTON_NO_ROLLBACK
- Removed checking of has_transaction_manager() in handler.cc as we can
  assume that as the transaction was started by the engine, it does
  support transactions.
- Added new class 'start_new_trans' that can be used to start indepdendent
  sub transactions, for example while reading mysql.proc, using help or
  status tables etc.
- open_system_tables...() and open_proc_table_for_Read() doesn't anymore
  take a Open_tables_backup list. This is now handled by 'start_new_trans'.
- Split thd::has_transactions() to thd::has_transactions() and
  thd::has_transactions_and_rollback()
- Added handlerton code to free cached transactions objects.
  Needed by InnoDB.

squash! 2ed35999f2a2d84f1c786a21ade5db716b6f1bbc

MDEV-21605 Clean up and speed up interfaces for binary row logging
MDEV-21617 Bug fix for previous version of this code

The intention is to have as few 'if' as possible in ha_write() and
related functions. This is done by pre-calculating once per statement the
row_logging state for all tables.

Benefits are simpler and faster code both when binary logging is disabled
and when it's enabled.

Changes:
- Added handler->row_logging to make it easy to check it table should be
  row logged. This also made it easier to disabling row logging for system,
  internal and temporary tables.
- The tables row_logging capabilities are checked once per "statements
  that updates tables" in THD::binlog_prepare_for_row_logging() which
  is called when needed from THD::decide_logging_format().
- Removed most usage of tmp_disable_binlog(), reenable_binlog() and
  temporary saving and setting of thd->variables.option_bits.
- Moved checks that can't change during a statement from
  check_table_binlog_row_based() to check_table_binlog_row_based_internal()
- Removed flag row_already_logged (used by sequence engine)
- Moved binlog_log_row() to a handler::
- Moved write_locked_table_maps() to THD::binlog_write_table_maps() as
  most other related binlog functions are in THD.
- Removed binlog_write_table_map() and binlog_log_row_internal() as
  they are now obsolete as 'has_transactions()' is pre-calculated in
  prepare_for_row_logging().
- Remove 'is_transactional' argument from binlog_write_table_map() as this
  can now be read from handler.
- Changed order of 'if's in handler::external_lock() and wsrep_mysqld.h
  to first evaluate fast and likely cases before more complex ones.
- Added error checking in ha_write_row() and related functions if
  binlog_log_row() failed.
- Don't clear check_table_binlog_row_based_result in
  clear_cached_table_binlog_row_based_flag() as it's not needed.
- THD::clear_binlog_table_maps() has been replaced with
  THD::reset_binlog_for_next_statement()
- Added 'MYSQL_OPEN_IGNORE_LOGGING_FORMAT' flag to open_and_lock_tables()
  to avoid calculating of binary log format for internal opens. This flag
  is also used to avoid reading statistics tables for internal tables.
- Added OPTION_BINLOG_LOG_OFF as a simple way to turn of binlog temporary
  for create (instead of using THD::sql_log_bin_off.
- Removed flag THD::sql_log_bin_off (not needed anymore)
- Speed up THD::decide_logging_format() by remembering if blackhole engine
  is used and avoid a loop over all tables if it's not used
  (the common case).
- THD::decide_logging_format() is not called anymore if no tables are used
  for the statement. This will speed up pure stored procedure code with
  about 5%+ according to some simple tests.
- We now get annotated events on slave if a CREATE ... SELECT statement
  is transformed on the slave from statement to row logging.
- In the original code, the master could come into a state where row
  logging is enforced for all future events if statement could be used.
  This is now partly fixed.

Other changes:
- Ensure that all tables used by a statement has query_id set.
- Had to restore the row_logging flag for not used tables in
  THD::binlog_write_table_maps (not normal scenario)
- Removed injector::transaction::use_table(server_id_type sid, table tbl)
  as it's not used.
- Cleaned up set_slave_thread_options()
- Some more DBUG_ENTER/DBUG_RETURN, code comments and minor indentation
  changes.
- Ensure we only call THD::decide_logging_format_low() once in
  mysql_insert() (inefficiency).
- Don't annotate INSERT DELAYED
- Removed zeroing pos_in_table_list in THD::open_temporary_table() as it's
  already 0