Leaders from some of the world’s largest emerging economies are gathering in New Delhi this weekend for a summit marking the 20th anniversary of Brics, a fast-expanding group of developing nations. Chinese President Xi Jinping, along with his Russian and Iranian counterparts Vladimir Putin and Masoud Pezeshkian, are among those meeting in the Indian capital for one of the group’s most closely watched gatherings in years. Brics can point to some achievements over that time, with analysts...