Leawood, Kan. — AMC Theatres, the largest theatrical exhibitor in the United States and in the world, has made a critical hire as it prepares to expand its business into the multibillion-dollar retail popcorn industry. Ellen Copaken, formally of Frito-Lay and Hostess Brands, will join AMC as the vice president, growth strategy, beginning February 18. In this newly created role, Copaken will lead AMC’s implementation of growth ideas related to the sale to consumers of popcorn outside AMC’s historic in-theatre channel. She will report to Mark Pearson, chief strategy officer, …