NEW YORK — Jon Stewart, America’s foremost satirist of politicians and the media, said goodbye to “The Daily Show” on Thursday, ushered out by Bruce Springsteen and a reunion of the many colleagues that he worked with during 16 years as host. “Guess what? Stewart said. “I’ve got big news. This is it.” Armed with a razor-sharp wit and research team adept at finding video evidence of hypocrisy or unintentional comedy among the nation’s establishment, Stewart turned a sleepy basic-cable entertainment show into a powerful cultural platform.