The first Oasis show in 16 years starts with “Hello,” amid scenes consistent with a riot. A continuous mosh pit thrashes through the center of Principality Stadium, from front to back and up into the stalls. Liam Gallagher is incandescent, his brow a triangular furrow; he yells at the mic as much as into it. “Hello, hello, it’s good to be back”—back in the 1990s. By the end of the set, legion fans and critics—those there at the very beginning—will hail it as the best Oasis show since the mid-’