Peter Debruge Chief Film CriticMaybe she was kidding, but director Clio Barnard recently described “Ali & Ava” as her shot at making a “social-realist musical.” The phrase, which slipped out during an interview from the BFI London Film Festival, struck me as some kind of oxymoron at first: How could a rugged, true-to-life depiction of a struggling working-class English couple possibly coexist with that most surreal of cinematic genres? But in light of the end result, Barnard’s ambition makes