Add Freestyle SITL

[MichelleRos]

Adds an FPV Freestyle type of quad (i.e. small and very low hover throttle, thus fast).

This one's max speed is slightly higher than real quads, probably because SITL doesn't seem to do battery sag (which is a lot on these copters) and because SITL doesn't have much noise, so all four motors can sit at nearly max throttle.

Currently a draft as I still want to improve some of the tuning.
Finished tuning so it's working well enough.

[peterbarker]

Looks like the tuning on this frame isn't good enough to allow the FlyEachFrame test to pass.

Should be able to run that test locally a few times to have it fail (it's the sort of thing that can flap).

... I've no idea why the autotest suite decided it was a good idea to stack-trace the process in the test output here, that's weird.

[MichelleRos]

Turns out that autotest wasn't loading the frame-specific defaults (eg freestyle.param) when using json frames, so autotest was using the default tune, which is very unflyable on this copter.

Rebased on master (with #26838) and then on top of #26839, and ran the FlyEachFrame test twice to check that it's now passing that test locally.

Thank you @peterbarker for figuring out the fix.