Add initial unfold animation prototype under feature flag

Introduces interfaces and classes for subscribing to hinge
update events, unfold transition progress controller that
uses dynamic animations to calculate current transition
progress. Added linear light reveal scrim overlay as an
example of transition progress subscriber.

Bug: 190818044
Test: manual
Change-Id: Ibf73a8c7dfa534432e0ed3ad637f0277bc7aafb9