Paddy Considine has played cops, ex-cons, priests, architects, struggling actors, union organizers and rock band managers. But when his agent told him that Ryan Condal and Miguel Sapochnik wanted him to play King Viserys I Targaryen in HBO’s “Game of Thrones” prequel series, “House of the Dragon,” he couldn’t quite believe it was real. “I said, ‘Who’s turned this down?’ Because I’m cynical that way,” he says. “My agent was like, ‘I assure you, they’re just coming to you for it.’” Part of Considine’s disbelief was due to his feeling that the industry at large had only ever seen him as the working-class striver he made his name playing in the 2000s, in films such as “In America,” “My Summer of Love” and “Cinderella Man.”