There were cases in the editor where rewinding of transforms would
leave the `DrawableHitObject` in a non-`IsPresent` state, resulting in
this scheduled logic never running.
This would in turn cause ghost hitobjects, which disappear under certain
circumstances.
Reproduction:
- Open editor to empty beatmap
- Place single hitcircle at current point in time
- Drag editor timeline backwards to seek before zero, and wait for
return to zero
- Select hitcircle in playfield
- Drag hitcircle to right in timeline, triggering a start time change
This was firing regardless of whether the start time was changed, such
as where beat snap provided the same time the object already has.
The case where a change actually occurs is already handled by
EditorBeatmap (see `startTimeBindables`), so it turns out this local
handling is not required at all.
This brings back the ability for the carousel to scroll in a classic
way. It turns out this is generally what we want for "seek" operations
like "random", else it's quite hard to get the expected animation.
I did experiment with applying the animation after the pooled panels are
retrieved, but in a best-case scenario there is still a gap where no
panels are displayed during the random seek operation.
In the case of automatic scroll requirements (ie. scroll to selected) we
are delegating the animation logic to the panels themselves. In order to
make this work correctly, the scroll operation needs to take effect
before any animation updates are run.
This was causing multiple issues with masking and sizing and really
didn't need to exist in the first place. Also not sure why the pool was
nested inside the scroll container, but it isn't any more. Probably for
the best.
