fix: set watchpack limit before loading watchpack

[chenjiahan]

Summary

We tried setting WATCHPACK_WATCHER_LIMIT by default in the Rspack CLI (#5486), but I found that this did not work because watchpack was loaded earlier than the WATCHPACK_WATCHER_LIMIT was set in the Rspack CLI.

This PR fixes the issue by setting WATCHPACK_WATCHER_LIMIT earlier in Rspack core.

Also submitted a PR to the watchpack repo: webpack/watchpack#249, if that gets merged we can remove this.

Checklist

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

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[codspeed-hq]

CodSpeed Performance Report

Merging #10236 will not alter performance

_{Comparing watchpack_limit_0429 (4189959) with main (d13413d)}

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Summary

✅ 11 untouched benchmarks