Consumer Reports is getting into the business of rating primary care doctors. The magazine is getting ready to mail out ratings for nearly 500 adult, family and pediatric physician practices in Massachusetts, the first step in a multistate project to evaluate doctors the way it has rated consumer products for decades. The ratings were drawn from patient surveys by Massachusetts Health Quality Partners, a coalition of physicians, hospitals and health plans that has been publishing data on physician performance on its website since 2006. The ratings are included in a 25-page insert to be mailed Thursday to the magazine’s 120,000 subscribers in Massachusetts.