Behold the smoothest-riding car in the world, and the quietest. Road Test Editor Howard Walker takes this SMOOTH OPERATOR: ‘21 ROLLS-ROYCE GHOST silent knight for a hushed spin. Wait, what happened to the bump? I clearly saw the gnarly, Detroit-style pothole looming fast. Waited for the ker-thump as a tire dropped into it. Waited for the thudder-judder in the steering.What happened was... nothing. Here, perched oh-so-stately behind the wheel of the all-new ‘21 Rolls-Royce Ghost, it seems...