MDEV-13918 Race condition between INFORMATION_SCHEMA.INNODB_SYS_TABLESTATS and ALTER/DROP/TRUNCATE TABLE

i_s_sys_tables_fill_table_stats(): Acquire dict_operation_lock
S-latch before acquiring dict_sys->mutex, to prevent the table
from being removed from the data dictionary cache and from
being freed while i_s_dict_fill_sys_tablestats() is accessing
the table handle.