Did you like “Mank” but really wish it was about “The Godfather” and not in black and white? And not directed by David Fincher? And not about “Citizen Kane?” Well, okay, maybe Barry Levinson’s upcoming film about the making of “The Godfather” doesn’t share too much with Fincher’s award-winning Netflix film, but they’re both about the making of classic films and they’re both getting pretty great casts.