Extra tests for MDEV-30483 After upgrade to 10.6 from Mysql 5.7 seeing "InnoDB: Column last_update in table mysql.innodb_table_stats is BINARY(4) NOT NULL but should be INT UNSIGNED NOT NULL"

Adding tests demonstrating that columns:
- mysql.innodb_table_stats.last_update
- mysql.innodb_index_stats.last_update

contain sane values close to NOW() rathar than a garbage.

Tests cover these three underlying TIMESTAMP data formats:

- MariaDB Field_timestamp0 - UINT4 based
  Like in a MariaDB native installation running with mysql56_temporal_format=0

- MariaDB Field_timestampf - BINARY(4) based, with UNSIGNED_FLAG
  Like in a MariaDB native installation running with mysql56_temporal_format=1

- MySQL-alike Field_timestampf - BINARY(4) based, without UNSIGNED_FLAG
  Like with a MariaDB server running over a MySQL-5.6 directory
  (e.g. during a migragion).