Blender Git Loki

LibOverride: fix/update/re-enable ID-related debug checks in diffing code.

We should now have the tools to ensure consistency of ID pointers
diffing in `rna_property_override_diff_propptr`.

As a reminder, for most ID pointers we just check the actual pointer value,
but this is not possible for embedded IDs like root node trees or master
collections, and for fake embedded ones like shapekeys, so those should be
handled as mere sub-data of their owner IDs in override context.