test all three OSes with both the latest and next-to-last system images and Py 3.8-3.12

[tngTUDOR]

Uses Github workflows to test

• [x] all three OSes with both the latest system images
• [ ] and next-to-last system images
• [ ] ~and Py 3.7~
• [x] and Py 3.9 -3.12.

[tngTUDOR]

@cmutel , OK to drop python 3.7 and only support >= 3.8?

[tngTUDOR]

next to last system images are identified at: https://github.com/actions/runner-images#available-images The ones to "add" on top of the ones we already test are:

• ubuntu-20.04
• macos-12
• windows-2019

[tngTUDOR]

macos-latest is macos-12, so we added macos-13 + macos-latest.