WASHINGTON - China’s next leader, Xi Jinping, may never have heard of American Superconductor Corp. before he arrived here Monday, but by the end of his visit U.S. officials hope to make the small Massachusetts wind-energy company an object lesson in the impact of Chinese trade secret theft on U.S. business. Sen. John Kerry, D-Mass., chairman of the Senate Foreign Relations Committee, plans to raise personally with Xi the case of a company that saw 70 percent of its business evaporate last year after a Chinese partner enticed one of its employees to steal the crown jewel of its technology.