In a covert crescendo, K-pop’s enigmatic maestros, Seventeen, have unveiled their 11th EP, “Seventeenth Heaven,” a hidden musical treasure that’s left the world in a state of auditory rapture. “Seventeenth Heaven,” a cryptic twist on “seventh heaven,” the pinnacle of happiness, as elucidated by their custodians at Pledis Entertainment, offers a glimpse into Seventeen’s world of clandestine creativity. How the …