Scott Carlin (Pete Davidson), the loser hero of “The King of Staten Island,” is a 24-year-old trash-talking punk stoner who lives with his mother in Staten Island and has no plans whatsoever — for a career, a life, or the next five minutes. He’s a slacker, a lout, and a self-pitying anger-management case who has never gotten over the death of his firefighter father 17 years ago.