1.5 Create a new wrapper using the Shell APIs.

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.

Bug: 397180418
Flag: EXEMPT unused for now, will be flagged upon usage
Test: atest ActivityTransitionAnimatorTest
Change-Id: I5192f1e834e20acfdc185712344247a4f2a77927