- Make a centralized reusable confirm dialog for Unsaved Changes in List Manager.
- Renamed the method setHasChangesMain to setHasUnsavedChangesMain in UnsavedChangesSource
- Refactor the changing of views methods to be centralized in ListManagerMain (saveAllListChangesAction(), discardAllListChangesAction(), cancelAllListChangesAction())

GCP-9350

Reviewer: Darla (Post-commit)