This also moves the beatmap skin disable toggle to on toggle, in line
with review feedback.
I've decided to always apply the disable, not just on the `Player`
screen. It should be assumed that if a user is in the skin editor they
are never going to need access to this anyway.
`GameplayClock` is inscrutable.
`TestManualClock` is lifted from another test scene because of
`FramedBeatmapClock`'s intensely confusing tendency to not work if it is
given a non-adjustable `ManuelClock` instead.
RFC. This is to allow notifications to show at the pause screen
(specifically for #23967, where exports are now happening).
Not sure about the break time part of this, but might be fine? The
toasts are immediately flushed before break time ends.