Cascade animation of users in switcher.

- Adds animations of user pods, page indicator, and username in user switcher.
- Adds delay between user pods to add cascading effect.

Bug: 36812644
Bug: 65423882

Change-Id: I369719d1d692c5b7414d33801007854d522882d8
(cherry picked from commit ca567d817f75da0bcfd5de29a33ded00bc737985)