Fix manually set default importances not printed

[MicahGale]

Pull Request Checklist for MontePy

Description

This fixes the bug where cells made from scratch almost never prints their importance in the output no matter if the importance were manually set (#892). Turns out that the parameter self._explicilty_set is set to True when the official setters are used, however, this value is never checked for formatting. To fix this was rather trivial.

However this issue brought up a question of behavior. In the test case cell.importance.all=1.0 is used on an unattached cell. It's assumed that this would set all importance. However, the documentation says that this only works on the particles in the problem. The code assumed that if the cell is not attached to a problem that cell.importance.all has no effect. This is rather intuitive. So I decided on the following behavior. Is this correct?

1. With no problem importance.all sets the importance for every (~37) particle types.
2. All particle importances are filtered first by problem.mode before printing. This is to avoid ~37 separate imp:X=1 clauses.

Finally, I noticed that in the tests for cell 4 only importance.neutron is set but the expected behavior is to print the default value for importance.photon. I decided to ignore this for now, and we can discuss.

I threw in a test to replicate #913, and found it passed. So two birds one stone.

All or Nothing infrastructure

As we discussed below cell importances have to be an all or nothing affair. How I decided to implement this was to make it an infrastructure that could be, but probably shouldn't be, used by any CellModifier class.

1. montepy.print_in_data_block has private getters and setters to set a boolean flag in a dictionary by class prefix.
2. Setup Importance._explicitly_set to be a property that update that problem level flag whenever changed.
3. Setup link_to_problem to update that flag appropriately
4. Updated the CellModifier logic to allow this flag to override the other logic.
5. Fixed a bunch of bugs that came up along the way (as it always does with importance).
6. Ensured that all particles in the problem, but not explicitly set by the user print the default value.

Dict like behavior update

In developing I thought Importance.items() would be helpful, so I added Importance.keys(), Importance.values() and Importance.items().

Fixes #892, fixes #913

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General Checklist

• I have performed a self-review of my own code.
• The code follows the standards outlined in the development documentation.
• I have formatted my code with black version 25 or 26.
• I have added tests that prove my fix is effective or that my feature works (if applicable).

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   • A large language model (LLM), including ones acting on behalf of a human

2. Were any large language models (LLM or "AI") used in to generate any of this code?

• Yes
  • Model(s) used:
• No

Documentation Checklist

• I have documented all added classes and methods.
• For infrastructure updates, I have updated the developer's guide.
• For significant new features, I have added a section to the getting started guide.

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Ensure that:

• This PR fully addresses and resolves the referenced issue(s).
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• 100% coverage of the patch is achieved, or justification for a variance is given.

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📚 Documentation preview 📚: https://montepy--921.org.readthedocs.build/en/921/

[MicahGale]

Doc build is failing due to a security restriction of a linkcheck. The URL is still valid.

[tjlaboss]

Wonderful.