feat(new_split_chunks): support reuseExistingChunk

[hyf0]

Related issue (if exists)

Related to #2991, but I need to add a test case for it in another PR to make sure solving the issue.

Summary

With reuseExistingChunk: true, Rspack would try to reuse chunks generated in CodeSplitting.

The test case reuse-existing-chunk-simple shows that the splittedFoo chunk is the same as foo_js chunk(generated in CodeSplitting), so we could just reuse the foo_js chunk instead of creating a new splittedFoo chunk.

🤖 Generated by Copilot at 5eff55d

This pull request adds a new option reuseExistingChunk to the split chunks plugin, which allows reusing existing chunks with the same modules instead of creating new ones. This option is enabled by default to improve performance and reduce bundle size. The pull request modifies the rspack_plugin_split_chunks_new crate and the rspack package to implement and expose the option. It also enables the let_chains feature in the rspack_plugin_split_chunks_new crate.

Walkthrough

🤖 Generated by Copilot at 5eff55d

• Add a new option reuseExistingChunk to the cache group configuration, which controls whether to reuse an existing chunk if it contains the same modules as the current chunk (link, link, link)
• Pass the value of the reuseExistingChunk option to the CacheGroup and ModuleGroup structs, which represent the cache group and the module group in the plugin logic (link, link, link)
• Enable the let_chains feature in the rspack_plugin_split_chunks_new crate, which allows using let expressions in the condition of an if or while statement (link)
• Import std::borrow::Cow to create a borrowed or owned reference to the chunks that the module group is related to (link)
• Modify the get_corresponding_chunk method in the plugin.rs file, which finds or creates a new chunk for a module group, to check if there is a reusable chunk and reuse it if the reuseExistingChunk option is true (link, link)
• Add a new method find_the_best_reusable_chunk in the plugin.rs file, which searches for the best existing chunk that can be reused for a module group based on the chunk name and the modules (link)
• Set the default value of the reuseExistingChunk option to true when converting a SplitChunksCacheGroup to a RawSplitChunksCacheGroup (link)

[changeset-bot]

🦋 Changeset detected

Latest commit: 5eff55d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 17 packages

Name	Type
@rspack/binding	Patch
@rspack/postcss-loader	Patch
@rspack/core	Patch
webpack-test	Patch
@rspack/cli	Patch
@rspack/dev-middleware	Patch
@rspack/dev-server	Patch
@rspack/plugin-html	Patch
benchmarkcase-rspack-react-refresh	Patch
@rspack/dev-client	Patch
@rspack/plugin-minify	Patch
@rspack/plugin-node-polyfill	Patch
@rspack/binding-darwin-arm64	Patch
@rspack/binding-darwin-x64	Patch
@rspack/binding-linux-x64-gnu	Patch
@rspack/binding-win32-x64-msvc	Patch
@rspack/fs	Patch

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