“ Ashes ,” a family drama about a young woman who leaves Mexico with her younger brother to reunite with their mother in Spain, was deeply personal to Diego Luna , who directs the film, in addition to co-writing its screenplay. Growing up in Mexico, Luna, best known for playing a swashbuckling rebel fighter in the “Star Wars” series “Andor,” had a deep understanding of the immigrant experience. “I live in a country that, because of the lack of opportunities, has a lot of people going to the