[flexiglass] Pin display polish.

This aligns the implementation closer to the go/android-u-bouncer-motion spec

- dots overshoot
- removing digits collapses them together with the shift animation
- clear all produces a staggered collapse effect

Bug: 282730134
Test: Manual verification. Please see video capture attached to b/282730134.
Test: Model unit tests
Change-Id: Ic3c2a257b4cac0fa81b0365e7da07798b342847b