Allow previewing audio of playlist items

[peppy]

Minimal implementation. Sizing of progress circle isn't great but functionality is there.

osu.2024-05-27.at.08.10.00.mp4

Addresses #21315.

[bdach]

How much should I be nitpicking the visuals? Because to me that looks... not great...

Progress circle aside:

• comically little padding between the preview thumbnail and the difficulty icon, especially compared to everything else on the playlist item having humongous amounts of padding
• track title / artist name having even less space to show than previously

[peppy]

track title / artist name having even less space to show than previously

I reduced the font size to allow for more to display (it was quite oversized before).

comically little padding between the preview thumbnail and the difficulty icon

it's using half the previous padding (looked okay to me). trying to strike a balance between padding and information density. can increase back to 8px if preferred.

[bdach]

it's using half the previous padding (looked okay to me). trying to strike a balance between padding and information density. can increase back to 8px if preferred.

We can reduce paddings but at the least if the difficulty icon is going to be that close to the preview, then the text on its right should be at least as close. Or the padding on the left should be slightly more, at the right padding's expense. Currently it just looks completely off imo.

[bdach]

I pushed one more visual change to fix this:

before	after

(look at relative alignment of the mapper text and the mod icons). Made apparent by the font size change no doubt.

Seems okay otherwise for a start I suppose