Oh, to be a rich teenager in the 1980s, says “The Shards” in so many words. Piling too much on too much is both Ryan Murphy and Bret Easton Ellis’ signature, however, as seen in this TV collaboration between auteur and author. “The Shards,” an adaptation of Ellis’ 2023 autobiographical novel, rewinds to his pre-“Less Than Zero” adolescence, when he was just Bret (Igby Rigney), a high school senior in lockstep with his hedonistic friends. When they aren’t snorting narcotics, everyone but Bret ignores evidence that a serial killer is circling ever closer. Bret may lament childhood’s demise, but if you had helicopter parents, these throes probably look less like trash than fire.