2.1 Create a new RemoteTransition using the new delegate directly.

Trying to make each of the CLs as small as possible to keep them
digestible and low risk. For the refactor plan see
go/animlib-shell-refactor-plan.

Additional tests exercising this class will be added when the full
flow is implemented.

Bug: 397180418
Flag: EXEMPT unused for now, will be flagged upon usage
Test: atest ActivityTransitionAnimatorTest
Change-Id: I674c8c532525afd08911a36ec0285b2a1224611e