“Spring 2023 is a celebration of people who are often unseen but monitored, watched, scrutinized,” Prabal Gurung said backstage about his spring collection show. “In this trying time — a slightly dystopian time, I think — hope and optimism was not enough, the vigilance, alertness is more. Where I found this refuge was when I went with my nephew to Brooklyn to a rave.…I had a feeling in my gut — if I’m…