Christopher Nolan is a busy man. When he’s not working on “The Odyssey,” his sprawling adaptation of Homer’s epic, he is tackling all the other challenges facing Hollywood as the new president of the Directors Guild of America. The union’s 20,000 members are dealing with a sharp decline in jobs, the rise of artificial intelligence, and the absorption of Warner Bros. into either Netflix or Paramount — which portends consolidation in streaming and a threat to the future of moviegoing. 'The