Libya’s United Nations-backed government blamed the United Arab Emirates for an airstrike that killed more than 50 people in Tripoli this week, suggesting a new level of foreign intervention in the battle for the capital. The U.A.E. used an American-made F-16 jet fighter in the strike, said Interior Minister Fathi Bashagha of the Government of National Accord, citing an assessment of the sound of the warplane’s engines and the size of the explosion. …