cda9440a29 inadvertently fixes this in the
most frequent case by inverting the `TickDistanceMultiplier` from being
not-1 to 1 on beatmap versions above v8.
This can still potentially go wrong if a beatmap from a version below v8
is edited, because upon save it will be reencoded at the latest version,
meaning that the multiplier will change from not-1 to 1 - but this can
be handled separately.
I've also removed inheritance from `SearchTextBox` because it contains
logic that might interfere with the internal implementation of dropdown
search bars (focus logic and stuff).
I thought this was already being handled, but it turns out that changing
sort mode (and potentially other operations) could break the depth of
display of panels due to pooling and what not.
This ensures consistency and also employs @bdach's suggestion of
reversing the depth above and below the current selection for a better
visual effect.