This class was only used in two places, both on the results screen, but
was holding references to `OsuPlayfield` game-wide (due to unrelated
issues, but still).
Because I can't really think of future use cases for this, and running
the calculation twice at results screen isn't a huge overhead, let's
just do that for now to keep things simple.
This avoids it ever mutating the underlying track (aka attempting to start
it). Resolves the one caveat mentioned in
aeef92fa710648d4a00edc523e13c17ac6104125.
The new implementation of `DecouplingClock` will not mutate the
underlying clock in any way (unless attempting to start it when
approaching from a negative time value).
This should be quite safe as a result.
As described in #24248, the workaround employed by
`GlobalActionContainer`, wherein it tried to handle actions with
priority before its children by being placed in front of the children
and not _actually containing_ said children, is blocking the resolution
of some rather major input handling issues that allow key releases to be
received by deparented drawables.
To resolve, migrate `GlobalActionContainer` to use `Prioritised`, which
can be done without regressing certain mouse button flows after
ppy/osu-framework#5966.