[Alerting]: namespace fixes (#34470)

* [Alerting]: forbid viewers for updating rules if viewers can edit

check for CanSave instead of CanEdit

* Clear ngalert tables when deleting the folder

* Apply suggestions from code review

* Log failure to check save permission

Co-authored-by: gotjosh <josue@grafana.com>

pkg/services/ngalert/store/database.go

@@ -3,8 +3,8 @@ package store
 import (
 	"time"
 
+	"github.com/grafana/grafana/pkg/infra/log"
 	"github.com/grafana/grafana/pkg/services/ngalert/models"
-
 	"github.com/grafana/grafana/pkg/services/sqlstore"
 )
 
@@ -28,4 +28,5 @@ type DBstore struct {
 	// default alert definiiton interval
 	DefaultIntervalSeconds int64
 	SQLStore               *sqlstore.SQLStore
+	Logger                 log.Logger
 }