LIZ LEE and BERNARD ORR MILLIONS of residents of China's southern manufacturing hub of Guangzhou were told on Wednesday to get tested for COVID-19, as infections topped two thousand for two days running in the city's worst outbreak so far. As local cases across China reached their highest level since April 30, authorities announced on social media that five districts representing more than half of Guangzhou's population of almost 19 million would need to undergo mass testing. The latest round of mass testing in Guangzhou comes as China battles a rebound in infections in several economically vital cities, including the…