In March, HBO released “It’s Me, Hilary: The Man Who Drew Eloise,” a documentary in which Hilary Knight, illustrator of the Eloise books, reflected on his life as an artist and his connection to the immensely popular series, which was written by Kay Thompson, a singer, actress, and writer. During a visit to Mr. Knight’s house in East Hampton, on a shy acre that feels much larger and a world away from the bustle of the Hamptons in summer, the courtly 88-year-old told a visitor