The Chinese government has faced several tests of its economic mettle in recent years. Each time investors could be sure of a muscular response, from the unleashing of credit booms to heavy intervention in financial markets.  But Beijing’s lack of support for Evergrande, the country’s largest real estate developer, is upending such expectations. The heavily-indebted company last week failed to make a scheduled $83.5 million interest payment on one of its $20 billion worth of dollar-d