“Barbie” and “Oppenheimer,” having been primed by “Top Gun: Maverick,” may have saved Hollywood from financial and cultural oblivion, but they don’t hold a candle to “Hundreds of Beavers” in terms of hardscrabble invention, independence of vision, and cinematic integrity. That, and none of those multimillion-dollar time-wasters have quite as many actors scuttering around in full-size animal suits.