Use WindowManagerProxy.getRotation to determine if rotation has changed

- Follow-up of http://ag/19559863 as Config diff on windowConfiguration does not work on 3P Launcher, so diff WindowManagerProxy.getRotation instead
- Also centralized Configuration diff logic into StatefulActivity

Bug: 240730723
Test: manual on 90/180 degree rotation in Launcher, RecentsActivity and 3P Launcher
Change-Id: Ib368ed5d749841a6873a03e2644608ff68885922