PARIS - The 18th century porcelain Yves Saint Laurent ate from, a Cartier watch he used to wear, the leopard-print couches and gilded chairs he lounged on: It's all to hit the auction blocks as the late French couturier's longtime partner liquidates their art-and-knicknack-filled residences. The sale, organized by Christie's from Nov. 17 to 20, is the follow-up to the blockbuster auction earlier this year of Saint Laurent and partner