Blender Git Loki

Using an iterator to go over objects, and use this for library_query

This is not the ideal iterator (it loops over the scene collection tree 3x).
One solution (I want to discuss with Bastien Montagne @mont29) is whether to store the *parent of a SceneCollection to help with that. That would speed things up, and cost less memory.

We do not even need to store it in the file, since it can be re-generated at read time