The `NodeCategory` system is not used by Blender anymore for a couple years
already. Instead of using an additional abstraction layer, we now just use a
normal menu. One benefit of the `NodeCategory` system was that it could be used
to populate the search. However, the search is now directly populated from the
menu anyway.
Fixes#115746.
Pull Request: https://projects.blender.org/blender/blender/pulls/132021