At a bar lined with indoor golf simulators in Rock Hill, South Carolina, Nalin Haley is posing for pictures with a procession of starstruck twentysomethings in blazers.It’s a humid evening in late March and we are at the kickoff event for the Tri-County Young Republicans, the organization that Nalin, the 24-year-old son of former South Carolina governor and U.S. ambassador to the UN Nikki Haley, launched in February. Featured guests include gube…