Alerting: update rule test endpoints to respect data source permissions (#47169)

* make eval.Evaluator an interface
* inject Evaluator to TestingApiSrv
* move conditionEval to RouteTestGrafanaRuleConfig because it is the only place where it is used
* update rule test api to check data source permissions

pkg/services/datasources/fake_cache_service.go

@@ -0,0 +1,31 @@
+package datasources
+
+import (
+	"context"
+
+	"github.com/grafana/grafana/pkg/models"
+)
+
+type FakeCacheService struct {
+	DataSources []*models.DataSource
+}
+
+var _ CacheService = &FakeCacheService{}
+
+func (c *FakeCacheService) GetDatasource(ctx context.Context, datasourceID int64, user *models.SignedInUser, skipCache bool) (*models.DataSource, error) {
+	for _, datasource := range c.DataSources {
+		if datasource.Id == datasourceID {
+			return datasource, nil
+		}
+	}
+	return nil, models.ErrDataSourceNotFound
+}
+
+func (c *FakeCacheService) GetDatasourceByUID(ctx context.Context, datasourceUID string, user *models.SignedInUser, skipCache bool) (*models.DataSource, error) {
+	for _, datasource := range c.DataSources {
+		if datasource.Uid == datasourceUID {
+			return datasource, nil
+		}
+	}
+	return nil, models.ErrDataSourceNotFound
+}