BRUSSELS — Europe is finally firing back at Elon Musk. Aerospace companies Airbus, Leonardo and Thales said Thursday they had reached a preliminary agreement to combine their space activities to create the kind of European champion that Commission President Ursula von der Leyen has envisaged. Announcing “a leading European player in space,” the companies said they would combine their satellite and space systems manufacturing into a €6.5 billion business that will employ around 25,000 people