SIMON LEWIS and MICHELLE NICHOLS VETERAN U.S. diplomat Jeffrey Feltman was named a special envoy for the Horn of Africa on Friday, as Washington looks to step up diplomatic efforts in a region hit by the conflict in Ethiopia's Tigray and other crises. Feltman also will lead international efforts to address tensions between Ethiopia and Sudan and around the Grand Ethiopian Renaissance Dam, Secretary of State Antony Blinken said in a statement. Fighting in Tigray, between rebels and government forces from both Ethiopia and its neighbor Eritrea, has killed thousands of people and forced hundreds of thousands more from their…