Implement work-profile infra in BasePreferenceController

- Add settings:forWork in xml
- Set mIsForWork based on xml attribute
- Delete WorkProfilePreferenceController and move its function to
BasePreferenceController

Fixes: 123376083
Test: Add work profile, go to Settings->System->Language&input,
UI should show work profile related items
Change-Id: Id2dcbb0e158c117cdfd363466a275f4e133c345e