In Suzanne Collins’s blockbuster trilogy, “The Hunger Games,” Panem President Coriolanus Snow is presented as a calculating, ruthless dictator bent on destroying the Mockingjay heroine, Katniss Everdeen. In Collin’s new novel, The Ballad of Songbirds and Snakes (Scholastic), we are introduced to an angst-ridden teenage Snow, forty years before the…