Add support for using Python 3.6 interpreters

[zanieb]

Applies a patch to use Python 3.6 compatible types in our vendored packaging implementation used in the interpreter query script. Adds Python 3.6 and 3.7 test coverage in CI.

Closes #7418

[codspeed-hq]

Merging this PR will not alter performance

✅ 5 untouched benchmarks

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_{Comparing zaniebot:claude/add-python-3.6-support-BsaGJ (09e6298) with main (17afca3)}

[codspeed-hq]

Merging this PR will degrade performance by 5.65%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 1 regressed benchmark
✅ 4 untouched benchmarks

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

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	resolve_warm_jupyter	74.9 ms	79.4 ms	-5.65%

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_{Comparing zaniebot:claude/add-python-3.6-support-BsaGJ (da0b202) with main (0507193)}

[geofft]

Drive-by comment without a full review: IMO it's not useful to check this file in, because it carries a risk of diverging from the actual patches to the .py files. I would simply rely on git history and the README (and maybe rephrase the README to emphasize that these are patched versions of the vendored files) and manually cherry-pick the patch when revendoring.

Alternatively, leave this file in, but don't commit the changes to the .py files in source control, and instead apply this file at build time.

[zanieb]

Hm I'm quite partial to checking it in so it's easy to apply in the future and very clear what changed. I'm pretty hesitant to deal with applying it at build time.

These files rarely change and we're a small team. I think optimizing for strictly preventing drift here is a bit silly.

[zanieb]

I'll write a script to perform the vendoring.

[charliermarsh]

I'm comfortable with this change. Do we have a clear guidance for whether it would constitute a breaking change to undo this in the future, given that it's not in our officially supported version list?

[zanieb]

I would say it is not a breaking change per our policy. I can make that clearer.