Allow delete marker replication from replica (#11566)

in the case of active-active replication.

This PR also has the following changes:

- add docs on replication design
- fix corner case of completing versioned delete on a delete marker
  when the target is down and `mc rm --vid` is performed repeatedly. Instead
  the version should still be retained in the `PENDING|FAILED` state until
  replication sync completes.
- remove `s3:Replication:OperationCompletedReplication` and
   `s3:Replication:OperationFailedReplication` from ObjectCreated 
  events type

pkg/event/name.go

@@ -80,7 +80,6 @@ func (name Name) Expand() []Name {
 			ObjectCreatedPost, ObjectCreatedPut,
 			ObjectCreatedPutRetention, ObjectCreatedPutLegalHold,
 			ObjectCreatedPutTagging, ObjectCreatedDeleteTagging,
-			ObjectReplicationComplete, ObjectReplicationFailed,
 		}
 	case ObjectRemovedAll:
 		return []Name{