Add the ability to change offset during gameplay

[peppy]

On stable, you are able to use the + and - keys to adjust beatmap offset during the first x seconds of gameplay, and during break time.

A similar feature should be implemented as some users rely on this.

Discussed in #25000

^{Originally posted by Bubbleman532 October 3, 2023}
Currently there's no way to quickly adjust offset mid-map as there is in stable. Being able to adjust offset using the +/- keys by 5/1ms during breaks was an incredibly useful feature in multiplayer if you were sightreading a map, and it being missing means players are forced to play through with a sub-optimal offset. It's also useful to have if a map intro is slow, so would lower time spent finding a map offset tremendously by not having to sit through the intro over and over.

As an aside, the pre-map offset slider should also have a way to be adjusted in +/-1ms increments, tho I can open up another feature request for this if the separation is needed.