Rosario Dawson's all in on Cory Booker for President in 2020, but she might be a little biased ... because she just confirmed with us ... they're in a serious, loving relationship!!! The actress was at the Reagan National Airport in D.C. Thursday when our guy quizzed her on what's been widely rumored -- she's the woman Booker referred to last month on the Breakfast Club when he said he was dating someone very special, while adding, "I got a boo." It didn't take much prodding before Dawson said it was true and began gushing over her man, calling him...