Add mixed-handler for unfold and mix in pip state

Add unfold to mixed-handler so that we can mix in updates
for other components. In this case, we update pip state
during unfold.

Bug: 286084821
Test: Unfold with a PiP
Change-Id: I872c8326dfa4662feecb45e2d2b4fd7b042a9123
Merged-In: I872c8326dfa4662feecb45e2d2b4fd7b042a9123