The noble profile of a solemn, aging Great Dane named Apollo dominates Scott McGehee and David Siegel’s The Friend, a movie nominally about the difficulties of caring for a pet in New York City. (And which seems like a perfect choice for the New York Film Festival, where it premiered this week.) Dog movies are a regular fixture of the cinematic firmament, but it’s rare for one to so invest itself in its central animal without trying to anthropomorphize it, to enter its mind and give it a voice.