When editing metadata, it's annoying that the editor returns to compose
mode when switching between difficulties. This fixes that fallacy.
Supersedes and closes https://github.com/ppy/osu/pull/36724.
These used to work because there was a huge blocking load operation,
which is now more asynchronous.
Note that the change made in `SongSelect` is not required, but defensive
(feels it should have been doing this the whole time).