fix: use index maps for concatenated export rendering

[JSerFeng]

Summary

• use FxIndexMap/FxIndexSet for ConcatenatedModule export rendering so definitions, unused exports, and inlined exports keep deterministic insertion order without sorting
• add a concatenate-modules regression case for deterministic export definitions and unused export comments

Related links

• Follow-up to fix: sort ConcatenatedModule export keys for deterministic builds #13425 (comment)

Checklist

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

[Copilot]

Pull request overview

This PR aims to ensure deterministic rendering of ConcatenatedModule export definitions and related comments by relying on insertion-ordered collections instead of sorting or unordered hash iteration, and adds a regression test to lock the behavior in.

Changes:

• Switch ConcatenatedModule export rendering to use FxIndexMap / FxIndexSet so iteration order is deterministic.
• Remove the now-unnecessary sort step when rendering __webpack_require__.d(exports, { ... }).
• Add a new concatenate-modules config case to assert deterministic export definition ordering and // UNUSED EXPORTS comment ordering.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
crates/rspack_core/src/concatenated_module.rs	Use insertion-ordered maps/sets to make export definition + unused/inlined export comment rendering deterministic without sorting.
tests/rspack-test/configCases/concatenate-modules/deterministic-export-comments/rspack.config.js	Test config enabling concatenation/usedExports/providedExports to exercise the rendering path.
tests/rspack-test/configCases/concatenate-modules/deterministic-export-comments/index.js	Regression assertion for deterministic rendered export definitions and unused export comments.
tests/rspack-test/configCases/concatenate-modules/deterministic-export-comments/root.js	Test module defining used/unused exports to validate ordering.
tests/rspack-test/configCases/concatenate-modules/deterministic-export-comments/dep.js	Small dependency used by the exported functions to ensure they’re retained/used.

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[codspeed-hq]

Merging this PR will not alter performance

✅ 34 untouched benchmarks

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_{Comparing JSerFeng:fy/use-indexmap-concatenated-exports (560961b) with main (c211dbe)}