Plane: ATT.DesPitch now reports actual target, not nav output

[Georacer]

Summary

This PR changes the logged quantity in ATT.DesPitch from Plane::nav_pitch_cd to the target value that actually gets passed to the pitch controller.

Details

Logging Plane::nav_pitch_cd in ATT.DesPitch gives the false impression that there's steady-state error in the pitch controller.

This PR improves log readability, as it already includes PTCH_TRIM_DEG and the contribution of KFF_THR2PTCH.

Plane::nav_pitch_cd is already logged in CTUN.

Testing

sim_vehicle.py was spun up and PTCH_TRIM_DEG=3 was set.
TAKEOFF mode was armed.

Before:
ATT.DesPitch and CTUN.NavPitch overlap.
Steady-state error is falsely logged.

After:
The three pitch quantites are clearly discernible.

[IamPete1]

What happens in modes where stabilize_pitch_get_pitch_out is not called, like manual?