Houdini: Load usd to SOPs directly

[BigRoy]

Changelog Description

Implement a SOPs level usdimport loader.

Additional info

This allows artists to directly load managed data into SOPs instead of having load a LOPs state first and then have a lopimport inside SOPs. Without that extra bunny-hopping the load logic here may be slightly faster for certain cases.

Testing notes:

1. Load a USD file to SOPs
2. Manage versions should also work (update)

[MustafaJafar]

This is cool!
It works on my side.