Alerting: Bump grafana/alerting and refactor the ImageStore/Provider to provide image URL/bytes (#70182)

* implement alerting.images.Provider interface in our ImageStore

* add URLExists() method to fakeConfigStore

* make linter happy

* update integration tests

pkg/services/ngalert/store/testing.go

@@ -9,10 +9,15 @@ import (
 	"github.com/grafana/grafana/pkg/services/ngalert/models"
 )
 
-func NewFakeImageStore(t *testing.T) *FakeImageStore {
+func NewFakeImageStore(t *testing.T, images ...*models.Image) *FakeImageStore {
+	imageMap := make(map[string]*models.Image)
+	for _, image := range images {
+		imageMap[image.Token] = image
+	}
+
 	return &FakeImageStore{
 		t:      t,
-		images: make(map[string]*models.Image),
+		images: imageMap,
 	}
 }
 
@@ -43,6 +48,17 @@ func (s *FakeImageStore) GetImageByURL(_ context.Context, url string) (*models.I
 	return nil, models.ErrImageNotFound
 }
 
+func (s *FakeImageStore) URLExists(_ context.Context, url string) (bool, error) {
+	s.mtx.Lock()
+	defer s.mtx.Unlock()
+	for _, image := range s.images {
+		if image.URL == url {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
 func (s *FakeImageStore) GetImages(_ context.Context, tokens []string) ([]models.Image, []string, error) {
 	s.mtx.Lock()
 	defer s.mtx.Unlock()