- refactor updateQuaternion() to compute the yaw jacobian directly (respecting the rotation sequence determination)
- fuseHeading()/fuseYaw321()/fuseYaw312() helpers are eliminated and now mag heading fusion and EV yaw fusion compute the innovation in place
- clear up logic for performing zero innovation heading fusion when quaternion variance exceeds threshold (no more _is_yaw_fusion_inhibited flag manipulation)
- when at rest continue fusing last static heading with very low variance even if other heading sources are active
- remove class _mag_sample_delayed
- update mag fusion call graph to use mag sample delayed functionally
- Ekf::resetMagHeading()
- use low pass mag directly, but check if valid (magnitude)
- MAG_FUSE_TYPE_INDOOR treat like auto if heading required
- introduces new parameter EKF2_PREDICT_US to configure the filter
update period in microseconds
- actual filter update period will be an integer multiple of IMU
