this
Also adds storyboard event priority support.
Closes #3043 Remove "AllowLeadIn" flag
Without doing this, GameplayClock can be left in an incorrect state after a seek (due to the userOffsetClock being its own FramedClock).
This lead-in is intended to specify a value before zero, not a value before the start time. Also removes an unnecessary ProcessFrame call (it happens within Seek itself).
Prevents potential multiple evaluations of enumerable.
# Conflicts: # osu.Game/Screens/Play/GameplayClockContainer.cs
This is a hotfix for incorrect framework behaviour. Closes #4442