Dead code cleanup:

part_info->num_parts usage was wrong and working incorrectly in
mysql_drop_partitions() because num_parts is already updated in
prep_alter_part_table(). We don't have to update part_info->partitions
because part_info is destroyed at alter_partition_lock_handling().

Cleanups:

- DBUG_EVALUATE_IF() macro replaced by shorter form DBUG_IF();
- Typo in ER_KEY_COLUMN_DOES_NOT_EXITS.

Refactorings:

- Splitted write_log_replace_delete_frm() into write_log_delete_frm()
  and write_log_replace_frm();
- partition_info via DDL_LOG_STATE;
- set_part_info_exec_log_entry() removed.

DBUG_EVALUATE removed

DBUG_EVALUTATE was only added for consistency together with
DBUG_EVALUATE_IF. It is not used anywhere in the code.

DBUG_SUICIDE() fix on release build

On release DBUG_SUICIDE() was statement. It was wrong as
DBUG_SUICIDE() is used in expression context.

https://jira.mariadb.org/browse/MDEV-26221
my_sys DYNAMIC_ARRAY and DYNAMIC_STRING inconsistancy

The DYNAMIC_STRING uses size_t for sizes, but DYNAMIC_ARRAY used uint.
This patch adjusts DYNAMIC_ARRAY to use size_t like DYNAMIC_STRING.

As the MY_DIR member number_of_files is copied from a DYNAMIC_ARRAY,
this is changed to be size_t.

As MY_TMPDIR members 'cur' and 'max' are copied from a DYNAMIC_ARRAY,
these are also changed to be size_t.

The lists of plugins and stored procedures use DYNAMIC_ARRAY,
but their APIs assume a size of 'uint'; these are unchanged.

The changes to galera.galear_var_replicate_myisam_on
in commit d9b933bec6061758c5d7b34f55afcae32a85c110
are omitted due to conflicts
with commit 27d66d644cf2ebe9201e0362f2050036cce2908a.

There are two fill_record() functions (lines 8343 and 8618). First one
is used when there are some explicit values, the second one is used
for all implicit values. First one does update_default_fields(), the
second one did not. Added update_default_fields() call to the implicit
version of fill_record().

FIXME: Part of the MDEV-20699 test is disabled due to
nonderterministic result.