A long and belated 16 years after his last film (“Little Children,” 2006), filmmaker Todd Field has returned with something of a masterpiece with “TÁR,” starring Cate Blanchett. A bold, audacious, uncompromising work, “TÁR” centers on power and all its forms, its transactional nature, and the way it’s seemingly granted and taken away with lighting speed in our modern world.