Harry Melling, known for his role as Dudley Dursley, has shed significant weight and is now starring in the film “Harvest,” while Devon Murray, who played Seamus Finnigan, has traded acting for running his own stables in Ireland. Meanwhile, Matthew Lewis, once the awkward Neville Longbottom, is unrecognizable and thriving as a podcast host and actor, with roles in “Avoidance.”