This is quite a breaking change, but I think it is beneficial due to the large amount of usage of this class.
I originally intended just to remove the allocations of the two delegates handling the `Changed` flow internally, but as nothing was really using the bindables for anything more than a general "point has changed" case, this felt like a better direction.
Intentionally not using `[Values]` as the scale modes can be applied to
the running game instance directly, rather than recreating it all over
again.
The same could be said for the notification overlay but not sure, seems
like something that should be considered at an `OsuGameTestScene` level
instead (whether the same game instance can be reused for further
testing).
Turns out we likely don't want this, as it means the testing user (using
a visual test browser) will not have access to their beatmaps. Can
revisit at a future date if the temporary files are still an issue.