Transfer Interpolator from TransitionSet to child Transitions

Bug: 74831546

TransitionSet interpolator was never being used in child
transitions. This transfers the interpolator by setting the
interpolator of the children as they are added or when the
interpolator is set. It also works for other settings:
epicenter, path motion, and propagation.

Test: Ie8ce23fe15e6193fdb2909606e442bd2912a4c5a
Change-Id: Ia9e35639f025d14c6497fa30abf75252ff3b1423