MDEV-4786 - merge 10.0-monty - 10.0

Fixed main.mysql--help failure.

mysql-test/r/mysqld--help.result:
  PFS_MAX_RWLOCK_CLASS was raised to 40 during the merge.

mysql-test/r/mysqld--help.result

@@ -1196,7 +1196,7 @@ performance-schema-max-file-handles 32768
 performance-schema-max-file-instances 1556
 performance-schema-max-mutex-classes 200
 performance-schema-max-mutex-instances 3282
-performance-schema-max-rwlock-classes 30
+performance-schema-max-rwlock-classes 40
 performance-schema-max-rwlock-instances 1724
 performance-schema-max-socket-classes 10
 performance-schema-max-socket-instances 179