ekf2: Fix EKF preflight check fail false positives
ekf2: Fix EKF preflight check fail false positives

Uses a relaxed yaw innovation check threshold for fixed wing vehicle that can recover from larger yaw errors after takeoff.
Replaces the peak hold with decay filtering applied to the magnetic yaw innovations with a conventional lowpass filter. This prevents mag heading innovation transients caused by preflight handling from failing the check, but catches persistent errors. Sign swapping of innovations due to angle wrapping is not a problem due to the way that innovations are calculated inside the EKF, so a simple LPF sufficient.

PX4/Firmware,dagar/Firmware,krbeverx/Firmware,PX4/Firmware,dagar/Firmware,acfloria/Firmware,krbeverx/Firmware,acfloria/Firmware,acfloria/Firmware,Aerotenna/Firmware,Aerotenna/Firmware,Aerotenna/Firmware,krbeverx/Firmware,acfloria/Firmware,dagar/Firmware,PX4/Firmware,dagar/Firmware,Aerotenna/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,PX4/Firmware,dagar/Firmware,acfloria/Firmware,krbeverx/Firmware,acfloria/Firmware,Aerotenna/Firmware,mje-nz/PX4-Firmware,Aerotenna/Firmware,Aerotenna/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,mje-nz/PX4-Firmware,dagar/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,PX4/Firmware