IN THE HEYDAY of Vietnam’s communist economy, comrades could expect their health care, education, housing and entertainment to be provided by the government. In the freeish-market Vietnam of today, those necessities are still purveyed by one dominant entity, albeit a capitalist one. Vingroup, the country’s biggest conglomerate, and its two listed subsidiaries, Vinhomes (a property developer) and Vincom Retail (which offers other…