unified-storage: Reduce calls to the user service (#102934)

* Create ListByIdOrUID in user service

* create UnstructuredToLegacyFolderList 

* update GetFolders to use list parser

* update GetDescendants to use list parser

* update UnstructuredToLegacyFolder to also make a single call to the user service

---------

Co-authored-by: Stephanie Hingtgen <stephanie.hingtgen@grafana.com>

pkg/services/folder/folderimpl/unifiedstore_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/grafana/grafana/pkg/services/apiserver/client"
 	"github.com/grafana/grafana/pkg/services/dashboards"
 	"github.com/grafana/grafana/pkg/services/folder"
+	"github.com/grafana/grafana/pkg/services/user/usertest"
 	"github.com/grafana/grafana/pkg/storage/unified/resource"
 	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/require"
@@ -93,7 +94,8 @@ func TestComputeFullPath(t *testing.T) {
 func TestGetParents(t *testing.T) {
 	mockCli := new(client.MockK8sHandler)
 	store := FolderUnifiedStoreImpl{
-		k8sclient: mockCli,
+		k8sclient:   mockCli,
+		userService: usertest.NewUserServiceFake(),
 	}
 
 	ctx := context.Background()
@@ -187,7 +189,8 @@ func TestGetParents(t *testing.T) {
 func TestGetChildren(t *testing.T) {
 	mockCli := new(client.MockK8sHandler)
 	store := FolderUnifiedStoreImpl{
-		k8sclient: mockCli,
+		k8sclient:   mockCli,
+		userService: usertest.NewUserServiceFake(),
 	}
 
 	ctx := context.Background()