Allow list of hatches to {bar, barh}

[dstansby]

PR Summary

Fixes #17758. This seemed pretty easy. I think there's room to add some helper functions to do the broadcasting and iterating for all of the rect properties, but perhaps that can be done elsewhere? First PR in a while, so apologies if I've got something wrong...

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

[story645]

This is great. Maybe https://matplotlib.org/gallery/shapes_and_collections/hatch_demo.html#sphx-glr-gallery-shapes-and-collections-hatch-demo-py can be updated to use this?
(Though honestly that example is not great...)

[dstansby]

Good idea - I updated that example and it's quite a bit better without having to loop through the bar patches individually.

[tacaswell]

Left a small suggested change for the tests (use the default style rather than classic style), but I am 👍 on this going in as-is as well.

I am glad my estimation of the difficulty was wrong :)

[tacaswell]

Also, welcome back @dstansby :)