Access overmap terrain by global coordinates, continues #5619

Code in game::vertical_move that create "AUTO: up/down" notes has been formatted and uses overmap buffer. The current code scans the whole overmap, this changes reduces this to 81x81 area, but that can be changed.

overmap::display_notes has been formatted and uses overmap buffer. It's now a static function and shows *all* notes on all overmaps and returns an absolute position.