This also makes loading consistent between ActorFrame, ActorScroller and DActorScroller.
Previously, we ran ActorFrame::LoadFromNode before adding children, which caused InitCommand
to be run before adding children.
ScreenCredits and ScreenRanking without constructing dozens or hundreds
of actors, which saves a lot of memory and is easier to manipulate. This could
also be used to support CourseContentsLists for long courses cheaply, etc.