Add a setting for lightening playfield only if beatmap has storyboard/video

[wooster0]

Implements https://github.com/ppy/osu/discussions/25003 but in a way that makes it more general and not as user-specific (https://github.com/ppy/osu/discussions/25003#discussioncomment-7181940).

As a 100% dim user, I can totally see myself using this when I feel like I want some animated visuals that are not just the same static thumbnail that I can see in the song select. With this setting I don't have to manually check whether a beatmap actually has anything interesting in the background that is not just the thumbnail and then adjust the dim (and then reset it to 100% when I'm done). Because at least for me, if there's just the thumbnail in the background I might as well just make the dim 100% so I can focus on the circles better.

https://github.com/ppy/osu/assets/35064754/c0e75a00-72ec-423c-8d6a-85cb164af661

(In this video the first beatmap which has no storyboard/video kept its dim at 100%; the second one which has storyboard/video had its dim reduced by 30%)

This does not have tests unfortunately because that didn't seem trivial. But because it's a minor feature, I hope it might be fine? If not, I will try more and possibly ask for help.

It was fun to make this so I accept that this might be rejected.

I also put two unrelated but very minor commits in this PR. I hope that's not a problem. The main commit is https://github.com/ppy/osu/commit/8c046d23b9d88c09b4a35f9b4b5c1352ca6775bf