MDEV-14825 Assertion `col->ord_part' in row_build_index_entry_low upon ROLLBACK or DELETE with concurrent ALTER on partitioned table

If creating a secondary index fails (typically, ADD UNIQUE INDEX fails
due to duplicate key), it is possible that concurrently running UPDATE
or DELETE will access the index stub and hit the debug assertion.

It does not make any sense to keep updating an uncommitted index whose
creation has failed.

dict_index_t::is_corrupted(): Replaces dict_index_is_corrupted().
Also take online_status into account.

Replace some calls to dict_index_is_clust() with calls to
dict_index_t::is_primary().

mysql-test/suite/innodb/t/alter_partitioned_debug.test

@@ -0,0 +1,34 @@
+--source include/have_innodb.inc
+--source include/have_partition.inc
+--source include/have_debug.inc
+--source include/have_debug_sync.inc
+
+CREATE TABLE t1 (a INT, b VARCHAR(10)) ENGINE=InnoDB
+PARTITION BY RANGE(a)
+(PARTITION pa VALUES LESS THAN (3),
+PARTITION pb VALUES LESS THAN (5));
+
+INSERT INTO t1 VALUES(2,'two'),(2,'two'),(4,'four');
+
+connect ddl,localhost,root,,test;
+SET DEBUG_SYNC = 'inplace_after_index_build SIGNAL go WAIT_FOR done';
+send ALTER TABLE t1 ADD UNIQUE KEY (a,b(3));
+
+connection default;
+SET DEBUG_SYNC = 'now WAIT_FOR go';
+BEGIN;
+SELECT * FROM t1 FOR UPDATE;
+SET DEBUG_SYNC = 'now SIGNAL done';
+
+connection ddl;
+--error ER_DUP_ENTRY
+reap;
+
+connection default;
+DELETE FROM t1;
+disconnect ddl;
+
+SET DEBUG_SYNC = 'RESET';
+
+CHECK TABLE t1;
+DROP TABLE t1;