expose a getThrottle for vehicles. save some calcs in AIWheeledVehicleControllerData

deletion cleanups

Engine/source/T3D/vehicles/vehicle.h

@@ -147,6 +147,7 @@ public:
    void onRemove() override;
 
    Point2F getSteering() { return mSteering; };
+   F32 getThrottle() { return mThrottle;};
    /// Interpolates between move ticks @see processTick
    /// @param   dt   Change in time between the last call and this call to the function
    void advanceTime(F32 dt) override;