I think this makes things a bit more readable. The only weird case is
the transfer of details from the component to the `OverlinedHeader`, but
bindables make it not too bad.
This is the general direction we're going with future designs. Just
applying this now because it makes a lot of screens feel much better
(multiplayer lobby / match, song select etc. where there are elements
adjacent to the bar which cause the transparency to feel a bit awkward).