Test whether panic button response still works on Android 10

Android 10 places new restrictions on background apps starting activities:

https://developer.android.com/guide/components/activities/background-starts

Test whether this affects the panic button response, which uses two invisible activities (PanicResponderActivity and ExitActivity), under the following circumstances:

Briar isn't running
Briar is running and visible in recent apps
Briar is running but not visible in recent apps