The “Scream” films have been self-referential ever since Drew Barrymore first picked up the phone to riff on scary movies with her killer, but “Scream VI” is the most meta entry yet, thanks to a climactic set piece in a Ghostface museum. Built in an old theater by a killer from an earlier “Scream,” the museum is filled with artifacts from the first five films in the series, from weapons and clothes to beer cups from the party scene in the original movie.