Use WebAclMiddleware instead of events to clear WebACL cache without delay

**Problem**
Because the `webacl.cache` service use events to clear cache, it is not cleared immediately. On the ObjectsWatchedMiddleware, we add to clear it ourselves after WebACL changes in order to avoid race condition.

**Proposal**
Use the WebaclMiddleware to clear cache immediately.

Locate WebAclMiddleware, the webacl.cache service, and ObjectsWatchedMiddleware, then trace how events currently clear the cache after WebACL changes. Verify where the middleware can perform immediate invalidation without the existing race condition. Done means WebACL cache updates no longer wait for event handling and the redundant manual clearing is removed or no longer needed.

Written by the indexing model from the issue text.