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>

src/modules/ekf2/EKF/fake_pos_control.cpp

@@ -84,6 +84,7 @@ void Ekf::controlFakePosFusion()
 				const bool is_fusion_failing = isTimedOut(aid_src.time_last_fuse, (uint64_t)4e5);
 
 				if (is_fusion_failing) {
+					ECL_WARN("fake position fusion failing, resetting");
 					resetFakePosFusion();
 				}