VelocitySmoothing - Refactor class to use polynomial evaluation instead of numerical integration

This solves many numerical issues when the trajectory is close to the
primary NE axes (small velocities). It is also more robust when dt is
large and has some jitter.

src/lib/FlightTasks/tasks/ManualAltitudeSmoothVel/FlightTaskManualAltitudeSmoothVel.cpp

@@ -155,7 +155,8 @@ void FlightTaskManualAltitudeSmoothVel::_updateSetpoints()
 
 	float pos_sp_smooth;
 
-	_smoothing.integrate(_acceleration_setpoint(2), _vel_sp_smooth, pos_sp_smooth);
+	// TODO: move before updateDurations
+	_smoothing.updateTraj(_time_stamp_current, _acceleration_setpoint(2), _vel_sp_smooth, pos_sp_smooth);
 	_velocity_setpoint(2) = _vel_sp_smooth; // Feedforward
 	_jerk_setpoint(2) = _smoothing.getCurrentJerk();