Focus, Nav: Merged bits from RangeSelect features to enable early manipulation of focus scope for styling purpose.

FocusScopeId is tracked by nav scoring/request and stored in result.
It's all rather WIP and we should reorganize the SetNavIDXXX functions fiasco at some point (soon?).
Didn't separate FocusScope from SelectionScope for now, will re-investigate this later, this is the minimum commit to be able to do some styling.