NEW YORK — As a child, Fred Hechinger dreamed of running away to join the circus. Levity suits the 25-year-old, despite his role as the tyrannical Emperor Caracalla in “Gladiator II.” While his year — which has included the highly praised “Thelma,” with June Squibb — has been “fun and busy,” Hechinger says, it also “feels in some ways like …