✨ feat(mq-lang): add url_decode builtin function

[harehare]

Adds a named url_decode(s) counterpart to url_encode(s). The underlying percent-decoding already existed for the @ :urid conversion operator; this exposes it as a directly callable function for symmetry.

[codspeed-hq]

Merging this PR will not alter performance

✅ 31 untouched benchmarks

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_{Comparing feat/builtin-url-decode (eda0f78) with main (e3d21e5)¹}

Footnotes

1. No successful run was found on main (3c052ad) during the generation of this report, so e3d21e5 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩