Consider VS Code cell metadata to determine valid code cells

[dhruvmanila]

Summary

This PR adds support for VS Code specific cell metadata to consider when collecting valid code cells.

For context, Ruff only runs on valid code cells. These are the code cells that doesn't contain cell magics. Previously, Ruff only used the notebook's metadata to determine whether it's a Python notebook. But, in VS Code, a notebook's preferred language might be Python but it could still contain code cells for other languages. This can be determined with the metadata.vscode.languageId field.

References:

• https://code.visualstudio.com/docs/languages/identifiers
• https://github.com/microsoft/vscode/blob/e6c009a3d4ee60f352212b978934f52c4689fbd9/extensions/ipynb/src/serializers.ts#L104-L107
• https://github.com/microsoft/vscode/blob/e6c009a3d4ee60f352212b978934f52c4689fbd9/extensions/ipynb/src/serializers.ts#L117-L122

This brings us one step closer to fixing #12281.

Test Plan

Add test cases for is_valid_python_code_cell and an integration test case which showcase running it end to end. The test notebook contains a JavaScript code cell and a Python code cell.

[MichaReiser]

Awesome, thank you.

I think it would be good to add a round-trip test case with additional CellMetadata.

[codspeed-hq]

CodSpeed Performance Report

Merging #12864 will degrade performances by 4.09%

_{Comparing dhruv/vscode-language-id (142de81) with main (899a523)}

Summary

⚡ 1 improvements
❌ 1 regressions
✅ 30 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	dhruv/vscode-language-id	Change
⚡	linter/all-rules[numpy/globals.py]	765 µs	726.4 µs	+5.31%
❌	linter/default-rules[pydantic/types.py]	1.8 ms	1.9 ms	-4.09%

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[dhruvmanila]

Added a simple roundtrip test case with additional cell metadata. I also tested it using ruff_dev round-trip notebooks/test.ipynb where the cell metadata isn't sorted and the output gives sorted metadata with all information intact.