Heavyweight opera behemoth /institution La traviata is always in need of agile, intelligent reworkings like Longborough’s intriguing new production. Daisy Evans’ incisive update makes Violetta Valéry a Hollywood filmstar in the late Fifties, taking inspiration from the celebrated, yet tortured life of Marilyn Monroe. While this has certainly been done before (memorably by Grange Park Opera in 2014), Evans’…