Will some serious star power reinvigorate the Cannes Film Market? That’s the big question facing sales agents as studios and streamers hit the Croisette on the prowl for compelling new movies. At Sundance, Berlin and Toronto, the movie business seemed to be in the throes of a massive contraction. Having spent freely while launching their own in-house challengers to Netflix, studios like Warner Bros., Disney and Paramount, along with their indie brethren, were in full-on cost-cutting mode. Complicating matters was the fact that after being burned by overspending for projects and packages at festivals in the past, tech giants like...