Update all apps fade interpolators for home <-> all app

Previously, predictions faded in quickly but then all apps faded in
linerally over entire rest of the transition. Now, all apps fades in
quickly after reaching the overview threshold where predictions are
opaque.

Also implemented the reverse, so that predictions/all apps content
remain opaque when returning home until reaching the overview threshold
near the bottom, where they fade out as quickly as they faded in.

We do this for 3-button mode as well.

Bug: 141986013
Change-Id: Ia35ab3ac9714e89f754293445a7839e15da5313d