RBAC: Refactor GetUserPermissions to use []accesscontrol.Permission (#50683)

* Return slice of permissions instead of slice of pointers for permissions

pkg/services/ngalert/api/api_alertmanager_test.go

@@ -368,7 +368,7 @@ func TestRouteCreateSilence(t *testing.T) {
 			name:    "new silence, role-based access control is enabled, authorized",
 			silence: silenceGen(withEmptyID),
 			accessControl: func() accesscontrol.AccessControl {
-				return acMock.New().WithPermissions([]*accesscontrol.Permission{
+				return acMock.New().WithPermissions([]accesscontrol.Permission{
 					{Action: accesscontrol.ActionAlertingInstanceCreate},
 				})
 			},
@@ -413,7 +413,7 @@ func TestRouteCreateSilence(t *testing.T) {
 			name:    "update silence, role-based access control is enabled, authorized",
 			silence: silenceGen(),
 			accessControl: func() accesscontrol.AccessControl {
-				return acMock.New().WithPermissions([]*accesscontrol.Permission{
+				return acMock.New().WithPermissions([]accesscontrol.Permission{
 					{Action: accesscontrol.ActionAlertingInstanceUpdate},
 				})
 			},