Handle destroyed sessions and fix color issues

When a media session is destroyed,
- Replace buttons with a single "restart" button that attempts to
restart the app (using media key event if we found a receiver for it, or the
session activity if not)
- For the carousel, give user the option to remove the card on long-press

Also fixes color issues when transitioning between tracks

Fixes: 143235163
Fixes: 144033638
Test: manual
Change-Id: Ie859aeb2fabfb1fc3eecf12fc1c19bb4cfa792d3