Once understood to be a critique of society’s overreliance on smart technology, this “Black Mirror” classic turns out to have much more to say about our current fixation with cultural reckonings. — In the third episode of “Black Mirror,” Netflix’s futuristic anthology series about the dangers and unintended consequences of new technology, humans are implanted with a chip that records everything they see, hear, and do. The chip, known as a grain, allows humans to access their recorded memories anytime they wish…