add bucket level S3 received/sent bytes (#15084)

adds bucket level metrics for bytes received and sent bytes on all S3 API calls.

cmd/peer-rest-server.go

@@ -538,6 +538,8 @@ func (s *peerRESTServer) DeleteBucketMetadataHandler(w http.ResponseWriter, r *h
 	globalReplicationStats.Delete(bucketName)
 	globalBucketMetadataSys.Remove(bucketName)
 	globalBucketTargetSys.Delete(bucketName)
+	globalNotificationSys.RemoveNotification(bucketName)
+	globalBucketConnStats.delete(bucketName)
 	if localMetacacheMgr != nil {
 		localMetacacheMgr.deleteBucketCache(bucketName)
 	}