Apply user checks on the specific endpoints in VUL-4.
Created by: LawnGnome
This essentially reverts 447e3f928483f248d245aa556281fe621eb262b5, and replaces it with a more specific implementation that doesn't break Batch Changes.
The most interesting part of this is probably the split in user types in the frontend: the user area now only requests public fields, with the other fields only being requested when the settings area becomes active.
Fixes #26063 (closed).