Short, majestically coiffed, with hooded eyes, an orange-tinted tan and the peevish impatience of an absolute monarch: that is Valentino Garavani, the Italian couturier known simply as Valentino, as he appears in Matt Tyrnauer’s documentary portrait, “Valentino: The Last Emperor.” Watching the movie is a little like gorging on chocolate and Champagne until that queasy moment arrives when you realize you’ve consumed far too much.
