Bug fix for setting nuclide categories on the `HexToRZThetaConverter`

[jakehader]

Description

Add mapping from the original core's nuclide categorization to the convert core within the HexToRZThetaConverter. This is important for lattice physics temperatures and was a bug.

Update the HexToRZThetaConverter type strings to leverage the Flags system.

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Checklist

• [x] The code is understandable and maintainable to people beyond the author.
• [x] Tests have been added/updated to verify that the new or changed code works.
• [x] There is no commented out code in this PR.
• [x] The commit message follows good practices.
• [x] All docstrings are still up-to-date with these changes.

If user exposed functionality was added/changed:

The following are not applicable for this change

• [ ] Documentation added/updated in the doc folder.
• [ ] New or updated dependencies have been added to setup.py.

[john-science]

Is this PR still active?

[jakehader]

Is this PR still active?

It's a draft because I haven't had time to get back to it. Still an important bug to fix but I got stuck