Support highlightable Settings homepage menu for 2-pane

1. Add a preference group adapter to perform highlighting
2. Add a class for mapping highlighable menu keys and preference keys
3. Add an API to determine if the screen is in split mode

Bug: 199017944
Test: manual, build
Change-Id: I8e3fe5fb96480a31ee0f3b3afb6ad78999d3d2bc