Filmmaker Steph Green has been on a lot of television sets, but rarely is a director given the task of tackling a human story of trauma, an explosive 1980s flashback, a weightless sequence set on a far-off moon, and a giant squid attack all in one episode. That’s the challenge Green was given for her Watchmen episode “Little Fear of Lightning,” but she saw it not as a difficult task but an opportunity to do pretty much everything in the span of one hour of television. Watchmen is one of the most critically acclaimed shows in recent memory, …