Add Panic button sound preference to panic gesture settings page.

Also renamed emergency_sos_* to panic_*. "emergency sos" is used by
other OEMs.

https://screenshot.googleplex.com/66097f3e-6aa0-4e2f-afb8-22f278bb0ed7.png

Bug: 161394591
Test: robotests
Change-Id: I14a59399fe7192d305d89a86dc93380c1e4c8a1c