Added new interpolator spec to be used throughout all of our motion

We're moving to a new version of interpolators which should be used
for all of our motion. The goal is to centralize all our interpolators
to a single place, such that we can update them all at once if we so
desire.

Bug: 197074707
Test: existing animations still look great, new interpolators work
Change-Id: I076535310bb1a4b0ff381067c6cf10cf285fbaa1