AUSTIN — The Stormy Daniels affair that in 2018 consumed Donald Trump’s presidency — after his attorney Michael Cohen violated the law by paying $130,000 to the adult-film star to keep silent — may feel like old news. But it’s far from over. And that was abundantly clear at this month’s South by Southwest premiere of the new documentary “Stormy,” where Daniels arrived as a surprise guest accompanied by two large security guards who surveyed the room at all times.