What is the change?

Historically, ARMI Flags have been all-caps and English Alphabet only: FUEL, DUCT``, FEED`, and so on. And if you added a numerical digit into the mix, it would be ignored (for various reasons).

This PR makes it so if the user defines a parameter it will be treated as an exception to the "letters only" rule, and handled exactly as-is.

This is only meant to support "upper case letters and numbers though". This PR still does not support flag names with:

• whitespace
• non-English characters
• special characters, like punctuation
• very long names

Why is the change being made?

This was a feature request made by downstream users.

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.