MDEV-20220: Merge 5.7 P_S replication table 'replication_applier_status_by_worker

Step 3:
======

Preserve worker pool information on either STOP SLAVE/Error.  In case STOP
SLAVE is executed worker threads will be gone, hence worker threads will be
unavailable. Querying the table at this stage will give empty rows. To
address this case when worker threads are about to stop, due to an error or
forced stop, create a backup pool and preserve the data which is relevant to
populate performance schema table. Clear the backup pool upon slave start.

mysql-test/suite/rpl/r/rpl_parallel_retry.result

@@ -127,6 +127,7 @@ include/wait_for_slave_sql_error.inc [errno=1213]
 SET GLOBAL debug_dbug=@old_dbug;
 retries
 10
+include/assert.inc [Performance Schema retries should match with actual retries]
 SELECT * FROM t1 ORDER BY a;
 a	b
 1	3