Amazon.com is considering a plan to open as many as 3,000 new AmazonGo cashierless stores in the next few years, according to people familiar with matter, an aggressive and costly expansion that would threaten convenience chains like 7-Eleven Inc., quick-service sandwich shops like Subway and Panera Bread, and mom-and-pop pizzerias and taco trucks.Chief Executive Officer Jeff Bezos sees eliminating meal-time logjams in busy cities as the best way for Amazon to reinvent the brick-and-mortar shopping experience, where most spending still occurs.