Track recents like home for times when it is separated

when using 3p launchers, recents is a separate stack. As
such we need to make sure that the recents root is provided
when asked for just like home is.

Bug: 158851728
Test: Using 3p launcher in split-secondary, open recents
Change-Id: I90dc6e75a718aa142c870b87bd93081e259acdea