UDITHA JAYASINGHE and DEVJYOT GHOSHAL SRI Lankan immigration officials stopped the president's brother and former finance minister Basil Rajapaksa from flying out of the country on Tuesday, as anger mounted over the island's worst economic crisis in decades. It was not clear where Rajapaksa, who also holds U.S. citizenship, was trying to go. He resigned as finance minister in early April as street protests surged against shortages of fuel, food and other necessities, and quit his seat in parliament in June. His elder brother, Gotabaya Rajapaksa, will resign as president on Wednesday to make way for a unity government, after…