“I have been a romantic for so long,” Romy Madley Croft sings on “I Dare You,” a post- R&B anthem from The xx’s third LP. But she changes gears a few lines later, boasting, “I’m on a different kind of high.” Both statements ring true on the hypnotic I See You, the London trio’s first album in five years, which balances their trademark broken-heart minimalism with lush,…