perf: use itoa for integer to string conversion

[shulaoda]

Summary

Related to rolldown/rolldown#2107

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

[shulaoda]

@chenjiahan cc

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[chenjiahan]

Nice 👍

[chenjiahan]

!bench

[rspack-bot]

📝 Benchmark detail: Open

Name	Base (2024-09-02 7b13eac)	Current	Change
10000_development-mode + exec	2.23 s ± 32 ms	2.24 s ± 42 ms	+0.13 %
10000_development-mode_hmr + exec	692 ms ± 21 ms	695 ms ± 13 ms	+0.54 %
10000_production-mode + exec	2.85 s ± 30 ms	2.82 s ± 27 ms	-0.95 %
arco-pro_development-mode + exec	1.86 s ± 57 ms	1.89 s ± 76 ms	+1.42 %
arco-pro_development-mode_hmr + exec	435 ms ± 3.5 ms	436 ms ± 2.6 ms	+0.15 %
arco-pro_production-mode + exec	3.27 s ± 89 ms	3.27 s ± 69 ms	+0.08 %
arco-pro_production-mode_generate-package-json-webpack-plugin + exec	3.35 s ± 85 ms	3.35 s ± 51 ms	0.00 %
threejs_development-mode_10x + exec	1.66 s ± 18 ms	1.66 s ± 21 ms	-0.32 %
threejs_development-mode_10x_hmr + exec	806 ms ± 13 ms	805 ms ± 6.5 ms	-0.10 %
threejs_production-mode_10x + exec	5.17 s ± 19 ms	5.16 s ± 33 ms	-0.14 %

[ahabhgk]

Thanks!