Introduce InterruptionHandler to STL

This CL introduces a new InterruptionHandler interface that allows to
specify what to do when a transition is interrupted and that we should
now animate to a new target scene.

When such an interuptions occurs, the caller can now specify 2
parameters of interruption:
 - animateFrom: the scene from which we animate to the new target scene.
   It must be either the fromScene or toScene of the interrupted
   transition.
 - chain: a boolean indicating whether the new transition is added to
   the list of current transitions (the default) or if all current
   transitions should be removed and that the new transition is the only
   remaining one in the list of ongoing transitions.

Bug: 290930950
Flag: N/A
Test: InterruptionHandlerTest
Change-Id: Ifebe37e5a35e304792aa602eb06212af3e6f1441