perf(incremental): better parallel for side effects plugin rebuild

[ahabhgk]

Summary

follow up #8799

Checklist

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

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[codspeed-hq]

CodSpeed Performance Report

Merging #8848 will not alter performance

_{Comparing inc-perf-side-effects (3a7ec5b) with main (93fc6ab)}

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Summary

✅ 3 untouched benchmarks