FIX: Make sure a renderer gets attached to figure after draw

[greglucas]

PR Summary

Make sure that a cached renderer gets added to the figure after calling fig.canvas.draw() on the macosx backend. This changes the draw path to go through adding a renderer to the figure first.

closes #19197
closes #13968
closes #7550

PR Checklist

Tests and Styling

• Has pytest style unit tests (and pytest passes).
• Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

• New features are documented, with examples if plot related.
• New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
• Documentation is sphinx and numpydoc compliant (the docs should build without error).

[tacaswell]

This is legacy from when the OSX backend was not Agg based, but was implemented on top of the OSX native drawing API. In that API we could only get a graphics context inside of the UI draw loop, hence we had to use draw_idle and force the UI event loop to spin. Now that the OSX backend is Agg based, we do not have this restriction and can make OSX behave more in line with the other Agg-based GUI backends.