Copter: parachute release is separate from crash-check allows possibility of parachute not being deployed in crash

The code for the regular crash-check is quite separate from the parachute release check.

They use almost exactly the same logic except that the parachute triggers after 1sec of loss of control while the crash-check triggers after 2 seconds. Also the parachute-check checks that the barometer says we're falling.

The separation of the logic means we're open to the possibility of the crash-check triggering without the chute deploying. Maybe that should be possible because we could imagine a simple flip on take-off (we might not want the parachute to deploy in this case).. but perhaps we should at least combine the logic and possibly delay the crash-check timeout if a parachute is installed (to give time to see if the vehicle is falling).

The issue names separate regular crash-check and parachute-release checks but no files, tests, or entry points. Locate both checks, compare their loss-of-control timeout and falling-state conditions, then clarify whether the intended behavior is combined logic, a delayed crash-check, or another agreed rule before defining completion tests.

Written by the indexing model from the issue text.