This is important when using dynamic compiling to rapidly iterate. Until we actually split projects out into pieces (like the abstract ruleset project we have talked about) there is no advantage to using internal in the osu! game code.
Also removes an unnecessary secondary list of SidebarButtons by using generic containers.
Most issues were related to BeginLoopedSequence usage and lack of "this." in front of transform helpers.
Also makes queueing of expand more correct.
Depends on https://github.com/ppy/osu-framework/pull/837