Add TABLE_SHARE::foreign_keys and TABLE_SHARE::referenced_keys as pointers to List<FOREIGN_KEY_INFO>.
Remove handler foreign key interface: get_foreign_key_list(), get_parent_foreign_key_list(), referenced_by_foreign_key().
Remove cached TABLE_SHARE objects of referenced tables when foreign table is dropped, renamed or altered (add foreign key, rename column of foreign key).
Remove cached TABLE_SHARE objects of foreign tables when referenced table is renamed or altered (rename column of referenced key).
Debug build: check consistency between opened foreign and referenced tables on table flush.