Supporting Python 3.12

[john-science]

What is the change?

This PR finally brings ARMI up to the Modern age, and supports Python 3.12.

There were two major dependency changes that needed different versions above and below Python 3.11 .

• ruamel
• h5py

Also, the unittest library no longer supports the long deprecated self.assertEquals(), just self.assertEqual() in Python 11.

Also, I had to make some rather obscure changes to how we use h5py to get it working in all versions of Python.

Why is the change being made?

It is important that ARMI support as wide a range of versions of Python and Python libraries as possible. This gives our downstream users flexibility to do what they want after they import armi.

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Checklist

• This PR has only one purpose or idea.
• Tests have been added/updated to verify any new/changed code.

• The code style follows good practices.
• The commit message(s) follow good practices.

• The release notes have been updated if necessary.
• The documentation is still up-to-date in the doc folder.
• The dependencies are still up-to-date in pyproject.toml.