These are the extremes that director Alejandro G. Inarritu navigates with audacious ambition and spectacular skill in “Birdman”–the full title of which is “Birdman or (The Unexpected Virtue of Ignorance).” He’s made a film that’s both technically astounding yet emotionally rich, intimate yet enormous, biting yet warm, satirical yet sweet. It’s also the first time that Inarritu, the director of ponderous downers like “Babel” and “Biutiful,” actually seems to be having some fun.