It’s been 20 years since Disney debuted the Nicolas Cage-headed action-adventure “National Treasure.” Watching that movie is like opening a time capsule from a prior civilization — one where our entertainment was agenda-free and just plain fun. Well, according to Cage, that time is long gone, especially at the House of Mouse. During a Tuesday interview with Screen Rant, Cage was asked about the possibility of returning to Disney for a third “National Treasure” film. “Here we go! See, you’re the one that brings these things up and they go out and they eclipse everything else,” Cage said, befor…