Sub-world partitions do not properly handle partial editor loading as world partition standalone level instances' spatially loaded actors do not get loaded even when the Level Instance is force loaded or loaded in by region.

Context
Level Instancing is a level-based workflow designed to improve and streamline the level editing experience. In a standalone Level Behavior, when the Level Instance Actor is loaded through its owning World Partition runtime cell, it loads the associated Level.

Problem
The problem is that world partition standalone level instances' spatially loaded actors do not get loaded even when the Level Instance is force loaded. According to the licensee, this also seems to affect world partition builder commandlets - in particular, navmesh generation doesn't work on standalone level instances unless partial loading is disabled.
The only suggested workaround is to disable partial loading with "wp.Editor.DisableLevelInstanceEditorPartialLoading 1".
Having partial loading disabled allows the spatially loaded cubes to show as expected.

1.) Download and open repro project uploaded in ticket
2.) Ensure level "L_TestMap" is opened (should be opened by default when opening project), if not go to Content Drawer > Content > L_TestMap
3.) Open World Partition Editor; Window > World Partition > World Partition Editor
4.) Right click the Loaded region and select Unload Selected Region
5.) Open Content Drawer and drag in L_TestInstance and move camera back / out to show 6 shapes (3 Cubes and 3 Spheres)
6.) In the outliner select L_TestInstance and in its details panel open the "Advanced" drop down menu in the "Level" Category, change Level Behavior to "Standalone" and make sure to Save after
7.) After saving, back in the outliner, Toggle Force Load on L_TestInstance to unload it, then toggle it once more to load it back in
Observe: The Cubes are not loaded in (These cubes are set to spatially load)
Expected: The cubes along with everything are loaded in