Navigator/FlightTaskAuto yaw handling improvements/simplifications (#22532)

* PositionSetpoint: remove yaw_valid field

* Navigator: set yaw setpoint to NAN for Takeoff

Don't set a yaw setpoint for takeoff, as Navigator doesn't handle the yaw reset.
The yaw setpoint generation is handled by FlightTaskAuto.

* PositionSetpoint.msg: remove disable_weather_vane and instead only use the yaw field

Strictly follow the concept that if the position_setpoint.yaw is set, then
follow it the controller, and otherwise let the controller set it as it
thinks it's best.

* Navigator: remove logic that sets yaw to be accepted in TAKEOFF

No longer needed as during Takeoff we anyway don't set a yaw setpoint.

* PositionSetpoint.msg: remove yawspeed_valid

* PositionSetpoint.msg: remove yawspeed

* Navigator: set yaw setpoint to NAN instead of current

In set_takeoff and set_land_item, as well as for VTOL transition.
The flight tasks then set the yaw corresponding to the current yaw.

* Navigator: change get_yaw_acceptance into a bool

* PositionSetpoint.msg: improve comment for yaw

* MissionBlock: remove unnecessary code from set_vtol_transition_item

* Navigator: clean up calculate_breaking_stop(), set yaw to NAN

* Navigator: set yaw to NAN in variouls places where not specifc setpoint is desired

* Navigator: set yaw to NAN in reset_position_setpoint()

---------

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>
Co-authored-by: Matthias Grob <maetugr@gmail.com>

src/modules/navigator/takeoff.cpp

@@ -130,7 +130,6 @@ Takeoff::set_takeoff_position()
 	mission_item_to_position_setpoint(_mission_item, &pos_sp_triplet->current);
 
 	pos_sp_triplet->previous.valid = false;
-	pos_sp_triplet->current.yaw_valid = true;
 	pos_sp_triplet->next.valid = false;
 
 	if (rep->current.valid) {