[Au2Ag4L4]2⊖, [Au2Cu4L4]2⊖, [Au3Cu3L4]2⊖, [Cu4L3]2⊖, and [Ag9L6]3⊖ (L = ethane‐1,2‐dithiolate)—Novel Homoleptic Complexes of the Coinage Metals, including the First Heteronuclear Metal Thiolates