Unistore : Ensure Watch works in HA mode (#94120)

* Revert "Revert "Unistore : Ensure Watch works in HA mode." (#94097)"

This reverts commit 7c3fc2f261.

* make previous_resource_version nullable

* handle nil case

pkg/storage/unified/sql/queries_test.go

@@ -104,6 +104,18 @@ func TestUnifiedStorageQueries(t *testing.T) {
 					},
 				},
 			},
+			sqlResourceHistoryPoll: {
+				{
+					Name: "single path",
+					Data: &sqlResourceHistoryPollRequest{
+						SQLTemplate:          mocks.NewTestingSQLTemplate(),
+						Resource:             "res",
+						Group:                "group",
+						SinceResourceVersion: 1234,
+						Response:             new(historyPollResponse),
+					},
+				},
+			},
 
 			sqlResourceUpdateRV: {
 				{
@@ -143,7 +155,8 @@ func TestUnifiedStorageQueries(t *testing.T) {
 					Data: &sqlResourceRequest{
 						SQLTemplate: mocks.NewTestingSQLTemplate(),
 						WriteEvent: resource.WriteEvent{
-							Key: &resource.ResourceKey{},
+							Key:        &resource.ResourceKey{},
+							PreviousRV: 1234,
 						},
 					},
 				},