By Anggy Polanco SAN ANTONIO DE TACHIRA, Venezuela/CUCUTA, Colombia (Reuters) -Colombia and Venezuela reopened cargo transport at a major border crossing on Monday, potentially enabling billions of dollars in trade after years of icy bilateral relations and heavily-restricted economic ties. The re-opening – which will allow goods like coal, toilet paper and fruit to move through crossings between the Colombian city of Cucuta and the Venezuelan state of Tachira – was a key campaign promise of Colombia’s new leftist President Gustavo Petro. Petro crossed the Simon Bolivar bridge on foot on Monda…