For the past decade, Dr. Priscilla Chan, along with her husband Mark Zuckerberg, have focused part of their philanthropy on a lofty goal — “to cure, prevent or manage all disease” — if not in their lifetime, then in their children’s. Now, the billionaire couple is shifting the bulk of their philanthropic resources to Biohub, the pair’s science organization, to focus on bringing together artificial intelligence and biology in an effort to accelerate scientific discovery.