BOSTON — Call it Boston’s latest Big Dig. Residents of Massachusetts woke up Wednesday to cars buried in several feet of snow, and secondary roads that remain covered in snow and narrowed by high snowbanks. But life is slowly returning to normal after a blizzard that left three feet of snow in some towns. TRAVEL A ban on non-essential travel has been lifted and Boston-area highways filled with traffic for the Wednesday morning commute. The MBTA resumed rail service, although weather-related delays on almost all subway and commuter rail lines were reported.