[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/tests/testinfra/testinfra.go

@@ -239,6 +239,12 @@ func CreateGrafDir(t *testing.T, opts ...GrafanaOpts) (string, string) {
 			_, err = anonSect.NewKey("plugin_admin_enabled", "true")
 			require.NoError(t, err)
 		}
+		if o.ViewersCanEdit {
+			usersSection, err := cfg.NewSection("users")
+			require.NoError(t, err)
+			_, err = usersSection.NewKey("viewers_can_edit", "true")
+			require.NoError(t, err)
+		}
 	}
 
 	cfgPath := filepath.Join(cfgDir, "test.ini")
@@ -257,5 +263,7 @@ type GrafanaOpts struct {
 	AnonymousUserRole    models.RoleType
 	EnableQuota          bool
 	DisableAnonymous     bool
+	CatalogAppEnabled    bool
+	ViewersCanEdit       bool
 	PluginAdminEnabled   bool
 }