Over lunch this month, two days after the Golden Globes ceremony and two weeks before the Academy Award nominations were announced, at Il Cantinori restaurant in Greenwich Village (shrimp scampi for Ms. Ronan and roast salmon for Mr. Chalamet), the pair discussed the eternal lure of coming-of-age films, the nostalgia (and worries) of young people, #MeToo on the red carpet and needing a break.