Added support for importing USD instanceable primitives into Blender
as collection instances.
Added a new USDInstanceReader class for importing USD
instances as Blender objects that instance collections containing
prototype data.
Extended the USDStageReader to read USD prototype prims into
collections that are instanced on the objects created by the instance
readers.
Removed the "Import Instance Proxies" import option.
Importing instances is enabled with a new "Scene Instancing" import
option, which is true by default. If this option is off, instances will be
imported as copies (which is the functionality previously enabled by
the "Import Instance Proxies" option).
Removed calls to UsdSkelBindingAPI::Apply() in the skeleton and
blend shape import code, as these calls were unnecessary and were
generating errors when importing instance prototypes with UsdSkel
data.
Nested instancing and animated prototypes are supported.
Pull Request: https://projects.blender.org/blender/blender/pulls/115076
ea89e11e01