Hide cursor during background reveal in song select

[UltraDrakon]

Addresses #36238

When using the background reveal feature, the cursor was intrusive and blocked the view of the beatmap background.

This PR makes the cursor fade out in sync with the background reveal animation. The behavior is:

• Cursor fades out when the background reveal starts
• Moving the mouse while viewing the background shows the cursor immediately
• After 1 second of no mouse movement, the cursor fades out again
• Cursor returns to normal when releasing the mouse button

[peppy]

If we're even considering allowing local control of cursor visibility using a new method, it needs to be lease based.

But more importantly, we have a system for hiding the cursor, see

osu/osu.Game/Graphics/Cursor/IProvideCursor.cs

Line 14 in 9b45a9c

public interface IProvideCursor : IDrawable

usages.

[peppy]

I'd recommend you attempt this again using IProvideCursor, hopefully with only a few lines of code.