Another casualty of edc78205d5312e9278f2a22ef156fd34af492595. This
particular button was actually *relying* on receiving positional events
from its entire bounding box rather than `Content`, in order for the
button to be htitable more easily, which broke as other buttons were
fixed to behave more in line with expectations.
Upon closer inspection this is another case of a weird carried-over
construction. The button doesn't really need to inherit `OsuButton` or
do any of the arcane stuff that it was doing, so it's now a plain
`OsuClickableContainer` with less `Content` hackery.
cebd5f6dc2