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.
- Only displays when required (there's literally zero case we want to
return input to the test, as this is automatic on next action)
- No longer hugs the right side of the screen (blocking visibility of
some tests).
This test scene passes at e58e1151f3 and
fails at current master, due to an inadvertent regression caused by
e72f103c17.
As it turns out, the online lookup flow that was causing UI thread
freezes when saving beatmaps in the editor, was also responsible for
resetting the online ID of locally-modified beatmaps if online lookup
failed.