Add two APIs
1. isActivityEmbedded() knows whether current activity is
embedded in the Settings app or not.
2. shouldHideBackButton knows whether current activity is
suggested to show back button or not.
Bug: 219000314
Test: Use the api in Settings app, and behavior is correct.
Change-Id: If1d29a8d9bdb896b179275e13de649872a5b94fe
This is an utility class to access relevant embedding activity feature
supported by Settings.
Bug: 201722672
Test: manual test
1) Run the apk built with this utils, and check some features work well
on large screen
Change-Id: I9f2a1fff57632ca2841b61a862f107d7df735247