We no longer want to maintain the separate OO.ui.PanelLayout this.outlineSelectWidget, but it's tightly coupled with the calling usages and with the event wiring.
- Remove this.outlineSelectWidget
- May require some changes to or even forking the OO.ui.OutlineControlsWidget
- findClosestPage will need to be rewritten.
- Rewire events which depended on this element.
- Refactor callers which depended on getOutline. For example, this.bookletLayout.getOutline().items.forEach will have to rely on a different data source for the items.