Ellise Shafer SPOILER ALERT: Do not read if you have not watched the first seven episodes of “Euphoria” Season 2. Despite the immense popularity of HBO’s “Euphoria,” clearing a song for use in the show isn’t as easy as it may appear — especially when it comes to legacy artists and estates.As music supervisor Jen Malone puts it, the teenage drama series has “sex, nudity, violence, drugs, guns. There’s not one thing that was missing as far as red flags for approval parties.”And yet the first episode of Season 2 kicks off with Billy Swan’s cover of “Don’t Be Cruel,” made famous by Elvis Presley.