Bookmarks don't show on real beatmaps, but they do show in test scenes
(namely `TestSceneEditorSummaryTimeline`).
Also does some more changes to adjust the markers to the latest updates
to other markers.
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.
