Detect automagic-like assignments in notebooks

[charliermarsh]

Summary

Given a statement like colors = 6, we currently treat the cell as an automagic (since colors is an automagic) -- i.e., we assume it's equivalent to %colors = 6. This PR adds some additional detection whereby if the statement is an assignment, we avoid treating it as such. I audited the list of automagics, and I believe this is safe for all of them.

Closes #8526.

Closes #9648.

Test Plan

cargo test

[github-actions]

ruff-ecosystem results

Linter (stable)

ℹ️ ecosystem check detected linter changes. (+0 -3 violations, +0 -0 fixes in 1 projects; 42 projects unchanged)

mlflow/mlflow (+0 -3 violations, +0 -0 fixes)

- examples/llms/RAG/question-generation-retrieval-evaluation.ipynb:cell 14:1:1: F821 Undefined name `df`
- examples/llms/RAG/question-generation-retrieval-evaluation.ipynb:cell 4:14:8: F401 [*] `requests` imported but unused
- examples/llms/RAG/question-generation-retrieval-evaluation.ipynb:cell 4:16:17: F401 [*] `bs4.BeautifulSoup` imported but unused

Changes by rule (2 rules affected)

code	total	+ violation	- violation	+ fix	- fix
F401	2	0	2	0	0
F821	1	0	1	0	0

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+0 -3 violations, +0 -0 fixes in 1 projects; 42 projects unchanged)

mlflow/mlflow (+0 -3 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --preview

- examples/llms/RAG/question-generation-retrieval-evaluation.ipynb:cell 14:1:1: F821 Undefined name `df`
- examples/llms/RAG/question-generation-retrieval-evaluation.ipynb:cell 4:14:8: F401 [*] `requests` imported but unused
- examples/llms/RAG/question-generation-retrieval-evaluation.ipynb:cell 4:16:17: F401 [*] `bs4.BeautifulSoup` imported but unused

Changes by rule (2 rules affected)

code	total	+ violation	- violation	+ fix	- fix
F401	2	0	2	0	0
F821	1	0	1	0	0

[charliermarsh]

Ecosystem checks are correct (i.e., they were false positives before the change).