[MM-57066][MM-57329] Added metrics for all notification stopping points, consolidated categories between metrics and logging (#26799)

* [MM-57066] Add metric counters for notification events

* Some small changes

* Account for Metrics() sometimes being nil

* Fix test (again)

* Fix more tests

* A few changes from testing - added success counter

* Missed a mock

* Lint

* Add feature flag for notification monitoring

server/channels/app/post_acknowledgements.go

@@ -42,11 +42,12 @@ func (a *App) SaveAcknowledgementForPost(c request.CTX, postID, userID string) (
 	}
 
 	if appErr := a.ResolvePersistentNotification(c, post, userID); appErr != nil {
+		a.CountNotificationReason(model.NotificationStatusError, model.NotificationTypeWebsocket, model.NotificationReasonResolvePersistentNotificationError)
 		a.NotificationsLog().Error("Error resolving persistent notification",
 			mlog.String("sender_id", userID),
 			mlog.String("post_id", post.RootId),
-			mlog.String("status", model.StatusServerError),
-			mlog.String("reason", model.ReasonFetchError),
+			mlog.String("status", model.NotificationStatusError),
+			mlog.String("reason", model.NotificationReasonResolvePersistentNotificationError),
 			mlog.Err(appErr),
 		)
 		return nil, appErr