“Party at LeBron’s” is a dynamite premise for a movie, especially if the King in question is the cheapskate egotist who stole the 2015 romcom Trainwreck as effortlessly as he would a lazy crosscourt pass. But it’s one thing for Judd Apatow and Amy Schumer to caricature the NBA great, quite another for James to take himself down a few pegs and bring one of the more beloved franchises in Black film cinema history with him.