Aria: DROP TABLE warns "uses an extension that doesn't exist" for a table with a fulltext parser plugin

INSTALL PLUGIN simple_parser SONAME 'mypluglib';

CREATE TABLE t1 (a TEXT, FULLTEXT(a) WITH PARSER simple_parser) ENGINE=Aria;

DROP TABLE t1;

Warning 1112 Table 't1' uses an extension that doesn't exist in this MariaDB version

maria_delete_table() opens the table with HA_OPEN_FOR_DROP | HA_OPEN_FOR_REPAIR to find out whether it is transactional. A table whose fulltext index uses a parser plugin is created with HA_OPTION_RELIES_ON_SQL_LAYER, and maria_open() refuses such a table unless HA_OPEN_FROM_SQL_LAYER is set, so it fails with HA_ERR_UNSUPPORTED. The files are still removed, but DROP TABLE returns the warning, and for a transactional table the REDO_DROP_TABLE record is not written to the Aria log.

It happens with any parser plugin; we found it while working on MDEV-10267 (ngram). MyISAM is not affected. The code is the same from 10.11 to main.

Proposed fix: let maria_open() accept HA_OPEN_FOR_DROP for such tables, since opening for drop only reads the share. We have the patch with an mtr test and will open a PR against 11.4 once this issue has a number.