Alerting: Time interval Delete API to check for usages in alert rules (#90500)

* Check if a time interval is used in alert rules before deleting it
* Add time interval to parameters of ListAlertRulesQuery and ListNotificationSettings of DbStore

== Refacorings == 
* refactor isMuteTimeInUse to accept a single route
* update getMuteTiming to not return err
* update delete to get the mute timing from config first

pkg/services/ngalert/models/notifications.go

@@ -18,8 +18,9 @@ const GroupByAll = "..."
 var DefaultNotificationSettingsGroupBy = []string{FolderTitleLabel, model.AlertNameLabel}
 
 type ListNotificationSettingsQuery struct {
-	OrgID        int64
-	ReceiverName string
+	OrgID            int64
+	ReceiverName     string
+	TimeIntervalName string
 }
 
 // NotificationSettings represents the settings for sending notifications for a single AlertRule. It is used to