[B&R] notify BackupManager when app optimization mode is changed

Invoke BackupManager.dataChanged() when app optimization mode is changed
to notify BackupManager to execute Settings agent to backup data in the
next backup session, when performing the partial backup event.

Bug: 192523697
Bug: 197608038
Bug: 194633034
Test: make SettingsRoboTests
Change-Id: I456acc2594d22503763e4ce286435148ae0644a4