Bubble v2 UI changes.

Including:
- Use exit-to-app icon instead of fullscreen icon for back-to-call button
- Use ripple for first button since it needs top-rounded background
- Change red hang-up button color and grey icon and text color
- Change some dimensions
Bug: 67605985
Test: manual
PiperOrigin-RevId: 176678427
Change-Id: I3f7836d832f7130f82d7f3764fb392807f3fab9a