feat: Add `get_attribute`, `set_attribute` `__getitem__` and `__setitem__` methods to `DefFrame`

[MarquessV]

Description

Closes #1710

Checklist

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

[rigetti-githubbot]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
7073	6201	88%	87%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
pyquil/quilbase.py	93%	🟢
TOTAL	93%	🟢

updated for commit: 56bd079 by action🐍

[MarquessV]

I'm not against this change, but wouldn't implementing the appropriate dunder methods be the "Pythonic" way to do this?

I went back and forth on that. I wanted to make it more clear that a bit of computation is going on (crossing the FFI and converting the value), though the guidelines don't really suggest any patterns around that. Since we were both thinking it, I'll go ahead and add it.