test: split incremental test cases to run in parallel

[LingyuCoder]

Summary

Since Jest can run in parallel only at the level of test files and can only execute serially within a single test file, the NewIncremental tests were split for parallel execution to reduce the test time consumption. The test on my machine was reduced from 150 seconds to 70 seconds.

Checklist

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

[netlify]

✅ Deploy Preview for rspack canceled.

Name	Link
🔨 Latest commit	bacc3df
🔍 Latest deploy log	https://app.netlify.com/sites/rspack/deploys/676d7c187b49c500086ff87e

[codspeed-hq]

CodSpeed Performance Report

Merging #8860 will not alter performance

_{Comparing test/split-new-incremental (bacc3df) with main (170b877)}

🎉 Hooray! codspeed-node just leveled up to 4.0.0!

A heads-up, this is a breaking change and it might affect your current performance baseline a bit. But here's the exciting part - it's packed with new, cool features and promises improved result stability 🥳!
Curious about what's new? Visit our releases page to delve into all the awesome details about this new version.

Summary

✅ 3 untouched benchmarks

[ahabhgk]

👍