Every Cannes Film Festival needs a film like “De Gaulle: Résistance,” a proudly French and massively scaled production with the energy of a vintage Hollywood blockbuster. Indeed, Antonin Baudry ’s old-fashioned epic flaunts all these big-screen qualities in delicious excess, dispensing a traditionally entertaining biopic on France’s eponymous Great Man and his consequential years in the early 1940s as an exiled general with a romantic vision of his country that has just capitulated to Germany.