Fix bug with operator precendence in iand and ior for geometry definitions

[MicahGale]

Pull Request Checklist for MontePy

Description

This fixes a bug with how __iand__ and __ior__ operate in HalfSpace. This bug is only apparent when intersections and unions are combined in a single expression. Quite frankly I don't understand the previous logic, and it was rather elaborate to handle the operations incorrectly. The notes in 4107b14 have better details:

• I honestly don't know what I was thinking previously this was so
  complicated and just wrong.
• The principle I used was that &= ands the new thing against
  everything.
  • i.e., (old) & new
• For example:
• If you have: existing geometry: +1:+2
  &= -3 should yield: (+1:+2)&-3
• For a binary tree this means:

           &
         /  \
        |    -3
       / \
      +1 +2

For testing the structure of mixed intersection and union definitions is actually tested. The string representation is also tested more, in part to make the test more readable. Finally, the export is tested with Cell.mcnp_str

Fixes #879

---

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.
• I have added tests that prove my fix is effective or that my feature works (if applicable).

---

LLM Disclosure

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.

---

First-Time Contributor Checklist

• If this is your first contribution, add yourself to pyproject.toml if you wish to do so.

---

Additional Notes for Reviewers

Ensure that:

• This PR fully addresses and resolves the referenced issue(s).
• The submitted code is consistent with the merge checklist outlined here.
• The PR covers all relevant aspects according to the development guidelines.
• 100% coverage of the patch is achieved, or justification for a variance is given.

---

📚 Documentation preview 📚: https://montepy--882.org.readthedocs.build/en/882/