Fix URL.host decoding for nested IDNA labels

[Abdulmumin1]

Fixes #850.

Summary

• decode IDNA labels that appear after ASCII labels in URL.host
• keep malformed punycode labels from leaking idna exceptions from the property
• add regression coverage for www.égalité-femmes-hommes.gouv.fr

[codspeed-hq]

Merging this PR will not alter performance

✅ 15 untouched benchmarks
⏩ 7 skipped benchmarks¹

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_{Comparing Abdulmumin1:fix-url-host-nested-idna (a5a6834) with main (c2a2b8d)}

Footnotes

1. 7 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[mbeijen]

you decode the complete host, you should probably try to decode each label and assemble them back together.

See the httpxyz fix at https://codeberg.org/httpxyz/httpxyz/src/commit/dc2bdf61f9d2061d89040dcd4babc1686c5de5bc/httpxyz/_urls.py#L194-L205

[Abdulmumin1]

thanks! i've updated accordingly

[Kludex]

I've opened kjd/idna#248 on idna's side. I don't think we should be handling it on our side.

I'll wait for their reply to take a decision here.