Sean Penn’s “Flag Day,” Leos Carax’s “Annette,” starring Adam Driver and Marion Cotillard, and Wes Anderson’s “The French Dispatch,” with Frances McDormand and Timothée Chalamet, will provide star power at a 2021 Cannes Festival packed to overflowing with established and very often new European and world cinema arthouse talent.The festival films will also drive much of Cannes’ business.