Blender Git Loki

Fix T93548: Appended (material) assets don't have a fake user

Since our design is to always keep data-blocks marked as assets on exit,
and our technical design for this is to do this via fake users, ensure
the fake user is set for an appended asset.

Reviewed by: Bastien Montagne

Differential Revision: https://developer.blender.org/D13443