Hilary Duff is a pop star once more. That is, if a pop star ever really stops being a pop star. Over 10 years since her last record — 2015’s “Breathe In. Breathe Out.” — Duff is back with “Luck… or Something,” a witty, and glittery, set of 11 pop songs that track the years that have passed since her teenage stardom. That brings existential questions, haunting what-ifs, some self-deprecating reflection and a healthy dose of cringe and nostalgia. Once a Disney Channel darling known best for