MDEV-22021: Galera database could get inconsistent with rollback to savepoint

When binlog is disabled, WSREP will not behave correctly when
SAVEPOINT ROLLBACK is executed since we don't register handlers for such case.
Fixed by registering WSREP handlerton for SAVEPOINT related commands.

mysql-test/suite/wsrep/r/trans.result

@@ -6,4 +6,5 @@
 #
 START TRANSACTION WITH CONSISTENT SNAPSHOT;
 SAVEPOINT A;
+ERROR HY000: Got error 1 "Operation not permitted" from storage engine binlog
 End of test.

mysql-test/suite/wsrep/t/trans.test

@@ -9,6 +9,7 @@
 --echo #
 
 START TRANSACTION WITH CONSISTENT SNAPSHOT;
+--error 1030
 SAVEPOINT A;
 
 --echo End of test.