wc: add a UTF-8 character-count benchmark

[darkraider01]

The existing character-count benchmark uses ASCII input. Add a UTF-8 case with two-, three-, and four-byte characters, plus instructions for running it in a UTF-8 locale.

Split from #15139 and #15140 as requested in #15140 (comment).

[sylvestre]

could you please set LC_ALL in the bench itself, like join_bench.rs or sort_locale_utf8_bench.rs?
codspeed won't use the env from the doc

[darkraider01]

done!

[sylvestre]

why -cm and not just -m like wc_chars_large_line_count?

[darkraider01]

done, thankyou

[codspeed]

Merging this PR will degrade performance by 14.95%

⚠️ 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

⚡ 2 improved benchmarks
❌ 1 regressed benchmark
✅ 396 untouched benchmarks
🆕 2 new benchmarks
⏩ 54 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	three_39_bit_primes	438.2 ms	761.9 ms	-42.49%
⚡	Simulation	five_38_bit_primes	1.9 s	1.8 s	+3.83%
⚡	Simulation	thirteen_39_bit_primes	9.1 s	8.8 s	+3.04%
🆕	Memory	wc_chars_utf8[100000]	N/A	16.6 KB	N/A
🆕	Simulation	wc_chars_utf8[100000]	N/A	767.1 µs	N/A

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing darkraider01:wc-utf8-benchmark (9d308ce) with main (33a2889)}

Footnotes

1. 54 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. ↩

[sylvestre]

Thanks for your PR