By Alex Lawler LONDON (Reuters) – Oil slumped almost 6% to its lowest in almost two weeks on Monday, extending last week’s decline as concern grew that prolonged COVID-19 lockdowns in Shanghai and potential increases in U.S. interest rates would hurt global growth and energy demand. In Shanghai, authorities have erected fences outside residential buildings, sparking fresh public outcry. In Beijing, many people have begun stockpiling food, fearing a similar lockdown after the emergence of a few cases of COVID-19. “It seems that China is the elephant in the room,” said Jeffrey Halley, analyst at…