Update Dark theme slice for new behavior

- Add an broadcast receiver to monitor the Home key.
- Add the sClickedInSlice flag to verify Dark theme is changed by slice or not.

Bug: 142476879
Fixes: 146149658
Fixes: 146652692
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.homepage
Change-Id: I174d0c861ea3b3f793201e3b2e0ff65a1e690f4e