Rename panic gesture in GestureLauncherService

Renamed panic to "emergency" or "emergency gesture" to
avoid speculation once source code is accessible to
people without full context.

Code names in other files will be updated separately

Bug: 171589858
Test: rebuild
Change-Id: I388b68b22a7134870d5a6ff3c69b7c91bfa11208
2 files changed