chore: Remove pydantic dependency

[mac01021]

Description

Insert your PR description here. Thanks for contributing to pyQuil! 🙂

Checklist

• The PR targets the master branch
• The above description motivates these changes.
• The change is atomic and can be described by a single commit (your PR will be squashed on merge).
• All changes to code are covered via unit tests.
• Parameters and return values have type hints with PEP 484 syntax.
• Functions and classes have useful Sphinx-style docstrings.
• (New Feature) The docs have been updated accordingly.
• (Bugfix) The associated issue is referenced above using auto-close keywords.

[MarquessV]

I think it's worth getting rid of Pydantic since we use it in such a limited way, and it should simplify dependency management for consumers of pyQuil. I have a few questions about leaning on built-in @dataclass behavior, and why some fields moved around, but I'm liking where this is heading.

For reference, some important places these models are used:

pyquil/quantum_processor/transformers/compiler_isa_to_graph.py
pyquil/quantum_processor/transformers/qcs_isa_to_compiler_isa.py
pyquil/noise_gates.py

[MarquessV]

If you rebase your branch, you should hopefully pull in a fix for the failed test check.

[MarquessV]

One place to cleanup an old comment, but LGTM!