ekf2: add simple zero velocity update when vehicle at rest (#19149)

- further decreases initial tilt alignment time (now down to 2.5 seconds if still) and improves initial bias estimates

src/modules/ekf2/EKF/estimator_interface.h

@@ -258,12 +258,7 @@ public:
 
 protected:
 
-	EstimatorInterface()
-	{
-		_control_status.flags.in_air = true;
-		_control_status.flags.vehicle_at_rest = false;
-	};
-
+	EstimatorInterface() = default;
 	virtual ~EstimatorInterface();
 
 	virtual bool init(uint64_t timestamp) = 0;