Ewan McGregor, for a fleeting moment after “Trainspotting” came out, felt like a rock star. It wasn’t his first significant project; it wasn’t even his first film with director Danny Boyle. And he was, in his words, fairly arrogant and cocksure at the time. But that kinetic film about four heroin addicts in late-1980s Scotland was and, 30 years later, remains defining — in his career, in the culture and in his understanding of what true artistic satisfaction can feel like. “It’s...