Group of 20 summit opened on Saturday with appeals by the world’s most powerful leaders to collectively chart a way forward as the coronavirus pandemic overshadows this year’s gathering, transforming it from in-person meetings to a virtual gathering of speeches and declarations.In a sign of the times, the traditional “family photo” of leaders in the summit was digitally designed and superimposed on a historical site just outside the Saudi capital, Riyadh, which would have hosted the gathering.