Tracking Push Notifications in a structured logger (notifications.log) (#10823)

* Remove NotificationRegistry table and use structured logging

* Fix ackId for notification sent

* Notification logger at server level

* Remove unused i18n strings

app/app.go

@@ -23,7 +23,8 @@ import (
 type App struct {
 	Srv *Server
 
-	Log *mlog.Logger
+	Log              *mlog.Logger
+	NotificationsLog *mlog.Logger
 
 	T              goi18n.TranslateFunc
 	Session        model.Session