Keep masking back in `Content`, since the scaling animation is happening
on `Content` instead of `this`. This doesn't regress the intended
behaviour in this PR (which is to just to make the button class itself
sheared instead of its content).
The sorting logic is now exercised in
`TestSceneSoloGameplayLeaderboardProvider`. Trying to work around
it with local test classes would mean that the test would be covering
test code, i.e. complete nonsense and having a green test for the sake
of having a green test.
As in, `https://osu.ppy.sh/multiplayer/rooms/{id}` links, clicked from
the chat overlay, now directly open in the client.
Additionally, `osu://room/{id}` can be used in the same way to open a
room from a third-party application or a browser.