Update turtle / crashflip mode (#13905)

* stop motors after 90 degrees of rotation and with max rate

* handle no accelerometer data

* improve check for acc, although seems to be OK without it

* disable all attenuation if rate is set to zero

* refactoring thanks Karate

* use sensors.h

* remove unnecessary arming check

* exit crashFlip immediately switch is reverted if throttle is zero

* add Crashflip Rate to OSD

* Revert unnecessary changes in crashflip core.c code

and clarify comments about crashflip switch

* update / minimise comments, thanks Karate

* ensure all names say `crashflip` consistently

* Undo quick re-arm because motrors were not reversed

* fix issue with reversed motors, we must disarm

* ignore yaw rotation and set gyro limit to 1900 deg/s

* default attenuation to off (crashflip_rate = 0)

* refactoring, increase rate limit to allow stronger inhibition

* enable in race_pro mode

* don't attenuate on attitude until a significant change occurs

* no attenuation for small changes

* Updates from review by PL

* remove whitespace

* refactor motorOutput, update comments, renaming variables

thanks PL

* changes from review PL

* only permit fast re-arm if crashflip rate set and crashflip was successful

* properly exit turtle mode

* add crashFlipSuccessful to unit test extern c

* small updates from review

* improved crashflip switch handling

* remove unnecessary motors normal check

src/test/unit/vtx_unittest.cc

@@ -211,4 +211,6 @@ extern "C" {
     void sbufWriteU16(sbuf_t *, uint16_t) {}
     void sbufWriteU32(sbuf_t *, uint32_t) {}
     void schedulerSetNextStateTime(timeDelta_t) {}
+    bool crashFlipSuccessful(void) {return false; }
+
 }