Cynthia Erivo as Elphaba and Ariana Grande as Glinda in “Wicked,” Courtesy of Universal Pictures “Wicked,” which has been beloved and enduring on the stage for 20 years, finally makes its long-awaited journey to the big screen as a spectacular and generation-defining cinematic event this holiday season. Cynthia Erivo (Harriet in Broadway’s “The Color Purple“)…