The odds of a new independent supermarket making it in a small New England town are long at best--especially when it sets up shop midway between a thriving Shaw's and Super Stop & Shop. But then the oddsmakers didn't figure on Jack Siravo. He's taken Belmont Fruit, his family's wholesale and produce business seasonal fruit stand, and turned it into Belmont Market, Wakefield, R.I.'s premier supermarket shopping experience.