fix(core): bump rslib and fix type related issues

[Timeless0911]

Summary

Improve @rspack/core declaration compatibility under moduleResolution: "nodenext".

• normalize prebundled declaration entrypoints for webpack-sources and watchpack
• keep Source and WatchOptions resolvable from bundled dependency declarations
• upgrade @rslib/core to 0.20.1 and adapt the emitted index.js/index.d.ts rewrites so Rspack.* namespace types remain accessible

Related links

• test: restructure type tests into separate resolution modes rsbuild#7333
• fix [Bug]: Source type resolves to any under moduleResolution: "nodenext" due to unresolvable ../compiled/webpack-sources import #13199

Checklist

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

[Copilot]

Pull request overview

This PR adjusts the @rspack/core prebundle configuration to normalize the generated declaration entrypoints for webpack-sources and watchpack, ensuring the emitted .d.ts filenames and package.json types field stay consistent.

Changes:

• Add helpers to rename copied .d.ts files and rewrite the bundled dependency package.json types field.
• Normalize webpack-sources declarations by renaming types.d.ts to index.d.ts and updating types.
• Enhance watchpack declarations by injecting a missing WatchOptions type export, preserving the graceful-fs @ts-ignore patch, and updating types.

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[github-actions]

Rsdoctor Bundle Diff Analysis

Found 5 projects in monorepo, 0 projects with changes.

📊 Quick Summary

Project	Total Size	Change
react-1k	826.2 KB	0
react-10k	5.7 MB	0
react-5k	2.7 MB	0
rome	984.2 KB	0
ui-components	2.3 MB	0

Generated by Rsdoctor GitHub Action

[github-actions]

📦 Binary Size-limit

Comparing 351cf67 to chore(ci): remove stale miri config (#13465) by neverland

🙈 Size remains the same at 48.97MB

[codspeed-hq]

Merging this PR will not alter performance

✅ 23 untouched benchmarks
⏩ 3 skipped benchmarks¹

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_{Comparing fix/prebundle-dts-entrypoints (351cf67) with main (1c683d6)}

Footnotes

1. 3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[chenjiahan]

LGTM