Blender Git Loki

Fix handling of overrides during append.

Liboverride references need a special handling during append, since
those pointers should never be made local, nor reampped to newly
localized data. And liboverride references should never be directly made
local either, to ensure their liboverride usages remain pointing to
linked data and not local one.

Issue was reported by the studio, and also probably as part of T91892.