Matt Donnelly Senior Film Writer HBO’s buzzy new original series “The Idol” has been steadily building momentum on the road to its June 4 debut — including a lavish world premiere at the Cannes Film Festival, followed by one of the most talked-about afterparties on the Croisette. The show follows an embattled young pop star named Jocelyn (Lily-Rose Depp), recovering from a psychotic break after the death of her mother and hounded relentlessly by industry vultures that need her back on top. A sketchy Svengali named Tedros (Abel “The Weeknd” Tesfaye) appears in her life, promising artistic and sexual liberation and fame beyond her wildest dreams. “Euphoria” creator Sam Levinson steers the show with co-creators Tesfaye and Reza Fahim.