came up (like how to align beat effects correctly). Revert this and
fix assist tick differently.
Add GetBeatAndBPSFromElapsedTimeNoOffset, GetBeatFromElapsedTimeNoOffset,
GetElapsedTimeFromBeatNoOffset. Use them to ignore GlobalOffsetSeconds.
given beat can have no more than one StopSegment or BPMSegment--more
than one just doesn't make sense. Split out TimingData::InsertRows,
TimingData::DeleteRows; delete rows in between before shifting data
up.
move sync display/saving out of complicated ScreenGameplay
show sync UI in editor playback as well as gameplay
revert sync from in-memory backup, not from disk
move more functions into debug overlay
Maybe we should stop calling note indexes "rows" and "indexes", and just
call them "beats"; if they're stored as an integer, they're in fixed-point. Things
like "note rows per second" are a lot less intuitive than just calling them "beats
per second".