On a March morning, in a suite at the Essex House, half a century ago, Muhammad Ali’s longtime friend and adviser Gene Kilroy received a call from the late Budd Schulberg, a writer whose contribution to the American canon includes “The Harder They Fall,” “On the Waterfront” and a line most famously recited by Marlon Brando but seemingly uttered by just about every failed fighter before or since: “I coulda been a contender.”