Bradley Cooper’s film “Maestro” premiered in Venice this fall, it seemed his moment of glory had finally arrived.The “Hangover” star’s direction of the prestige drama and his performance as famed “West Side Story” composer and conductor Leonard Bernstein were greeted enthusiastically by critics. The pretentious historical movie is, of course, the sort of thing the press tends to rubber-stamp automatically.The picture is about a real person; a big chunk of it was shot in black and white; the main character leads a secret gay life in New York City and ages some 40 years over the course of the story.