Straightforward Synthesis of 6-Aryl-2-azido-4-(trifluoromethyl)pyrimidines and Their Regioselective Copper-Catalyzed Click Cycloaddition to 6-Aryl-2-(4-phenyl-1H-1,2,3-triazol-1-yl)-4-(trifluoromethyl)pyrimidines