Prime Minister of New Zealand Jacinda Ardern addresses the 77th session of the United Nations General Assembly, Sept. 23, 2022, at the U.N. headquarters. (Julia Nikhinson/AP) WELLINGTON, New Zealand — New Zealand Prime Minister Jacinda Ardern, who became a global icon of the left and exemplified a new style of leadership, said Thursday that she would leave office. Just 37 when she became leader, Ardern was praised around the world for her handling of the nation’s worst-ever mass shooting and the early stages of the coronavirus pandemic. But she faced mounting political pressures at home and a level of vitriol...