“He’s the most idolized comedian ever,” Jerry Seinfeld says in the new trailer for “Steve!” a new documentary from Academy Award-winning filmmaker Morgan Neville Neville (“20 Feet from Stardom,” “Won’t You Be My Neighbor?”) about the beloved American national treasure Steve Martin. “He reinvented stand up,” another off-screen talking head says, and you know you’re in store for a doc that sounds and looks like it’ll be as entertaining as it is ebullient in its praise of the “Only Murders in The Buildings” star.