_set_view_from_bbox is called to figure out the new axes limits when the
mouse is released in interactive zoom.

• In the common zoom-in case, simplify the code by using set_x/ybound
  which maintains the previously existing axes inversion (if any),
  rather than having a bunch of conditions to sort the arguments
  correctly before passing them to set_x/ylim.

• In the (more rarely used?) zoom-out case (which is triggered by
  right-clicking, and zooms the axes out so that the previous axes
  limits fit in the drawn box), use the axis transform directly rather
  than just special-casing log-scale; this is necessary to make zoom-out
  work for other scales such as logit.

• Tiny cleanups to the len(bbox) == 3 case, which is only used by
  toolmanager to implement zoom-by-scroll, but isn't used by the default
  toolbar zoom.

Also add a test for this previously untested path.

PR Summary

PR Checklist

• Has Pytest style unit tests
• Code is Flake 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way