Enhance InstanceMap and ChangeBatcher for unresolved Ref properties

- Added `onInstanceInserted` callback to `InstanceMap` to notify when new instances are tracked, allowing `ChangeBatcher` to resolve pending unresolved Ref properties.
- Updated `createPatchSet` and `encodePatchUpdate` to support handling unresolved Ref properties, deferring their resolution until the target instance is available.
- Implemented logic in `ChangeBatcher` to manage pending unresolved Ref properties and re-queue them when the target instance is inserted.
- Introduced new tests to verify behavior with ambiguous paths and ensure stability when handling duplicate-named siblings.

These changes improve the handling of Ref properties in the system, enhancing synchronization reliability and robustness.

rojo-test/serve-tests/ref_ambiguous_path/src/Workspace/DupParent/Child.model.json5

@@ -0,0 +1,3 @@
+{
+  "className": "Part"
+}

rojo-test/serve-tests/ref_ambiguous_path/src/Workspace/DupParent/Child~1.model.json5

@@ -0,0 +1,4 @@
+{
+  "className": "Part",
+  "name": "Child"
+}

rojo-test/serve-tests/ref_ambiguous_path/src/Workspace/DupParent/init.meta.json5

@@ -0,0 +1,3 @@
+{
+  "className": "Model"
+}

rojo-test/serve-tests/ref_ambiguous_path/src/Workspace/Target.model.json5

@@ -0,0 +1,3 @@
+{
+  "className": "Part"
+}

rojo-test/serve-tests/ref_ambiguous_path/src/Workspace/init.meta.json5

@@ -0,0 +1,3 @@
+{
+  "ignoreUnknownInstances": false
+}