WL#7034: Deprecate and remove mysql_convert_table_format

This Perl script enables swapping storage engines for groups of tables.  That
probably predates I_S, which makes similar scripts far easier:

shell> mysql --batch -e"SELECT CONCAT('ALTER TABLE `', table_schema, '`.`',
table_name, '` ENGINE = InnoDB;') AS `#sql` FROM information_schema.tables
WHERE table_schema LIKE 'test';" | mysql

The suggestion is to deprecate and remove MYSQL_CONVERT_TABLE_FORMAT.

BUG#69014 Deprecate mysql_convert_table_format