After releasing his third studio album, “People Watching,” in February, Sam Fender played to a crowd of 82,500 at London Stadium, headlined three shows at his hometown’s St. James’ Park and even toured a few U.S. cities in the spring — but not Boston. In fact, Fender had never played a show in Boston before Wednesday, so when the northern Englishman finally announced the New England tour stop alongside additional U.S. dates on May 27, it was to much anticipation: The general sale sold out instantly.