KeyguardBottomArea: migrates to Expandable

Uses Expandable instead of ActivityLaunchAnimator.Controller which
allows future configs to open a dialog instead of an activity.

Fix: 243408565
Test: unit tests all pass. Manually verified on device that home
controls and wallet buttons still open their activities properly.

Change-Id: I967b7fb75e34c5e2aea6bed818fd957c5f70fad6