Description
-----------
WL#12820 now rewrites the GRANT Statements in the binlogs in case if
--partial_revokes is ON. It causes a few MTR test failures on the builds where
partial_revokes is ON.

Fix
---
- We already have a test file grant_as_ddl.test that verifies the grant rewrites
  in the binlogs. Therefore, we could skip printing the AS <...> WITH <...>
clause
  in the GRANT statement.
- Introduced a flag $mask_grant_as_events for the file show_binlog_events.inc
  file

Review
------
RB#21574