ekf2: separate mag and mag heading control logic (#21212)

- split mag_3d into new standalone mag fusion and mag fusion allowed to update all states (full mag_3d)
 - new dedicated control logic for mag/mag_3d fusion and standalone mag heading fusion
 - if WMM available use for mag_I and mag_B init
 - mag states reset if external yaw reset (yaw estimator, GPS yaw, etc)
 - mag reset if declination changed (eliminate _mag_yaw_reset_req)
 - mag fusion (but not mag_hdg or mag_3d) can be active during gps_yaw or ev_yaw (if yaw aligned north)

Co-authored-by: bresch <brescianimathieu@gmail.com>

msg/EstimatorStatusFlags.msg

@@ -39,6 +39,8 @@ bool cs_rng_kin_consistent      # 31 - true when the range finder kinematic cons
 bool cs_fake_pos                # 32 - true when fake position measurements are being fused
 bool cs_fake_hgt                # 33 - true when fake height measurements are being fused
 bool cs_gravity_vector          # 34 - true when gravity vector measurements are being fused
+bool cs_mag                     # 35 - true if 3-axis magnetometer measurement fusion (mag states only) is intended
+bool cs_ev_yaw_fault            # 36 - true when the EV heading has been declared faulty and is no longer being used
 
 # fault status
 uint32 fault_status_changes   # number of filter fault status (fs) changes