Restore editor mode when changing difficulty

[peppy]

When editing metadata, it's annoying that the editor returns to compose mode when switching between difficulties. This fixes that fallacy.

Supersedes and closes #36724.

[bdach]

Just to confirm: this was attempted once in #36724. You tried to touch that PR up but then ended up adding a lot of schedule stuff in 4067b11 that I took issue with in review.

This doesn't have any of that, and is considerably simpler as such, but then may have an issue of multiple screen loads.

What am I to do at this point?

[peppy]

You have a better memory than I.

Let's see how tests look on this and go with it if you/tests don't break it. There's a weird flicker when loading but it's not enough to outweigh the usability improvement, and I'm not really interested in fixing it for now.

I'm kinda interested in recent times in getting the actual core issues fixed and then worrying about the more minor details (like two screens maybe being loaded unnecessarily) later on.