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{

pkg/event/name_test.go

@@ -32,8 +32,7 @@ func TestNameExpand(t *testing.T) {
 		{BucketRemoved, []Name{BucketRemoved}},
 		{ObjectAccessedAll, []Name{ObjectAccessedGet, ObjectAccessedHead, ObjectAccessedGetRetention, ObjectAccessedGetLegalHold}},
 		{ObjectCreatedAll, []Name{ObjectCreatedCompleteMultipartUpload, ObjectCreatedCopy, ObjectCreatedPost, ObjectCreatedPut,
-			ObjectCreatedPutRetention, ObjectCreatedPutLegalHold, ObjectCreatedPutTagging, ObjectCreatedDeleteTagging,
-			ObjectReplicationComplete, ObjectReplicationFailed}},
+			ObjectCreatedPutRetention, ObjectCreatedPutLegalHold, ObjectCreatedPutTagging, ObjectCreatedDeleteTagging}},
 		{ObjectRemovedAll, []Name{ObjectRemovedDelete, ObjectRemovedDeleteMarkerCreated}},
 		{ObjectAccessedHead, []Name{ObjectAccessedHead}},
 	}