`AllowDeselectionDuringDrag` is remove.
Instead, selected hit objects are not automatically deselected
when clock is seeked to a later time (the hit object is dead).
Update drag box selection even if mouse is not moved
(in case clock is running or scroll wheel is used).
This causes the focal point zooming to not work (as the focal point is
lost). There's no need to handle ongoing changes to
`BeatmapInfo.TimelineZoom` because it is not a property which is changed
at runtime.