On Feb. 25, 1964, Cassius Clay (Eli Goree) knocks out Sonny Liston to become the heavyweight champion at age 22. Afterward, Cassius, Malcolm X (Kingsley Ben-Adir), Jim Brown (Aldis Hodge), and Sam Cooke (Leslie Odom Jr.) get together at the Hampton House Hotel for an evening of conversation. Believe it or not, these four icons truly did meet that night, and screenwriter Kemp Powers (based on his play) imagines their discourse in a mesmerizing, intricate feature that leaves you hanging on every word. Most of director Regina King’s film transpires…