This fixes an issue where a CacheFile was always created for the USD
file, causing USD_create_handle() to be called unnecessarily even if the
USD does not have animating meshes or transforms.
This bug would sometimes result in the stage remaining open in a
CacheArchiveHandle after import (because the CacheFile is never
freed), preventing the USD from being reloaded from disk.
The cache file is now accessible to readers through an
ImportSettings::get_cache_file function wrapper which creates a
CacheFile as needed, the first time the function is called.
The allocated CacheFile pointer is now stored in a new
ImportJobData::cache_file member.
Pull Request: https://projects.blender.org/blender/blender/pulls/116242
3fc97a3ed4