* added logic to track spawning of sub blueprints
* added ability to determine when a blueprint instance is truly ready
(aka all its assets have been loaded, blueprint scene & sub scenes spawned & processed etc)
* reworked spawning steps for more determinism & reliability
* no more "seperate" spawning post process
* lots of related changes
* still messy but functional
* Blender: some additional component filtering for upgrade ui
* Bevy:
* experimenting with overhauled blueprint spawning logic, sub-blueprint instance tracking etc
* added a more simple blend file to test things out with
* added additional test "upgreadeable components"
* added test "buggy" hierarchies: blueprint instances as children of empties and blueprint
instances as children of other blueprint instance
* more materials
* testing cases for various levels of nesting/ targets for components
* reorganized objects in 3d scene for more clarity
* changed camera view for more clarity
* added background color & filmic
