Throughout Norwegian filmmaker Joachim Trier’s humanist, candid and melancholy Oslo-set romantic drama, “The Worst Person in the World,” you may find yourself wondering who the titular character might be. Is it Julia (Renata Reinsve), the indecisive, impulsive, entrancing heroine at the center of the story? Is it Aksel (Anders Danielsen Lie), Julia’s older boyfriend, a brilliant, edgy comic book artist? Is it the sweetly submissive Eivind (Herbert Nordrum) one of Julia’s other suitors? The truth is that none of them are “the worst” even if they may, at times, feel that way; indeed it’s their f…