unistore: replace CDK backend with KV store backend (again) (#113184)

* Reapply "unistore: replace CDK backend with KV store backend"" (#113132)

This reverts commit 7127b2538c.

* enable cluster scope

pkg/storage/unified/resource/server.go

@@ -1072,7 +1072,7 @@ func (s *server) List(ctx context.Context, req *resourcepb.ListRequest) (*resour
 
 			pageBytes += len(item.Value)
 			rsp.Items = append(rsp.Items, item)
-			if len(rsp.Items) >= int(req.Limit) || pageBytes >= maxPageBytes {
+			if (req.Limit > 0 && len(rsp.Items) >= int(req.Limit)) || pageBytes >= maxPageBytes {
 				t := iter.ContinueToken()
 				if iter.Next() {
 					rsp.NextPageToken = t