perf: lazy require browserslist package

[chenjiahan]

Summary

In most cases, Rspack does not need to require the browserslist package, it is only be used if target contains "browserslist".

Lazy require browserslist can make Rspack startup 17ms faster.

• before:

• after:

Checklist

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

[netlify]

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[chenjiahan]

!bench

[rspack-bot]

📝 Benchmark detail: Open

Name	Base (2024-09-24 ce775cc)	Current	Change
10000_development-mode + exec	2.22 s ± 47 ms	2.27 s ± 41 ms	+1.96 %
10000_development-mode_hmr + exec	687 ms ± 7.8 ms	707 ms ± 16 ms	+2.92 %
10000_production-mode + exec	2.8 s ± 38 ms	2.92 s ± 29 ms	+4.28 %
arco-pro_development-mode + exec	1.84 s ± 83 ms	1.84 s ± 70 ms	+0.07 %
arco-pro_development-mode_hmr + exec	434 ms ± 1.9 ms	437 ms ± 2.7 ms	+0.76 %
arco-pro_production-mode + exec	3.25 s ± 61 ms	3.32 s ± 81 ms	+2.23 %
arco-pro_production-mode_generate-package-json-webpack-plugin + exec	3.32 s ± 67 ms	3.36 s ± 82 ms	+1.27 %
threejs_development-mode_10x + exec	1.68 s ± 21 ms	1.71 s ± 13 ms	+1.32 %
threejs_development-mode_10x_hmr + exec	781 ms ± 7.9 ms	787 ms ± 18 ms	+0.72 %
threejs_production-mode_10x + exec	5.11 s ± 31 ms	5.27 s ± 29 ms	+3.05 %