Chris Willman Senior Music Writer and Chief Music Critic On the eve of heading up to Canada this week to attend the Toronto Film Festival, where his documentary “Lil Nas X: Long Live Montero” has its world debut Saturday night, pop superstar Lil Nas X was playing it nonchalant about stepping outside the music realm a bit to be the center of a splashy event in the movie world. “Not really,” he answers, when asked whether it means anything special to him to have a gala premiere at North America’s biggest film event. “I mean, I’m excited to go there and to see what people think, and also, I’ve never been to a film festival, so maybe I’ll meet people and and build some future relationships.