Library sidebar: allow moving focused index with Ctrl + Up/Down

[ronso0]

follow-up for #11208, just the last commit.

Move focused index with Ctrl + Up/Down. Left/Right also work without Ctrl.
It's now consistent with the track view, see #11100

I find it handy for browsing history playlists without mouse, like when I want to check which History logs contain a certain track (need to keep the current tracks view obviously). If I find an interesting setlog, I just press Enter/Return to load it.

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Draft for now as it requires yet unreviewed #11208

[github-actions]

This PR is marked as stale because it has been open 90 days with no activity.

[daschuer]

The code looks good. Need to test. Can you resolve conflict, by rebase if you like.

[ronso0]

Yeah, will do.
I noticed a sidebar selection issue in my personal branch (with this branch merged) lately, but couldn't reproduce it, yet. I'll observe this and figure whether it's in 2.4 or this branch or only in my branch.

For me this is low prio currently, and IMO it can go to 2.4 at any time as bug fix because it restores consistency of tracks table & sidebar.
So I suggest you don't spend your valuable time on this one until I'm sure it's save. Don't want to introduce regressions with this fix that probably only very few users will discover anyway.

I'd rather appreciate if we could get #11527 (and #11695 as follow-up) merged asap.

[github-actions]

This PR is marked as stale because it has been open 90 days with no activity.