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

✅ 7 untouched benchmarks

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_{Comparing Abdulmumin1:fix-url-host-nested-idna (9bac192) with main (d0e0f37)}