MDEV-22811 DDL fails to drop and re-create FTS index

Problem:
========
- InnoDB clears the fts resource when last FTS index is being dropped
if the table has user defined FTS_DOC_ID. While creating the new fts
index, InnoDB expects to have FTS resources.

Fix:
===
fts_drop_index(): Removed the fts resource clear.

fts_clear_all(): Clear the fts resource when there are no new fts
index to be added.

commit_cache_norebuild(), row_merge_drop_indexes():
Tries to call fts resource after removing associated fts index
from table object

mysql-test/suite/innodb_fts/t/innodb-fts-ddl.test

@@ -270,3 +270,11 @@ SELECT * FROM articles WHERE MATCH (title, body)
 	AGAINST ('Tutorial' IN NATURAL LANGUAGE MODE);
 
 DROP TABLE articles;
+
+--echo #
+--echo # MDEV-22811 DDL fails to drop and re-create FTS index
+--echo #
+CREATE TABLE t1 (FTS_DOC_ID BIGINT UNSIGNED PRIMARY KEY,
+		 f1 VARCHAR(200),FULLTEXT fidx(f1))engine=innodb;
+ALTER TABLE t1 DROP index fidx, ADD FULLTEXT INDEX(f1);
+DROP TABLE t1;