[WIP] Add new metadata API

[milesj]

Description

A handful of Vite plugins mutate arguments of plugin functions, primarily through renderChunk and generateBundle, to support the internal viteMetadata structure, which tracks asset/css information for chunks.

While this currently works in rollup, this won't work in rolldown, as function calls and their arguments/return are serialized/deserialized when going across the Rust <-> JS bridge. This is non-trivial to support, so it's best that we avoid this pattern all together.

As a replacement, I'm introducing a general metadata store through the MetadataManager, which can be accessed within plugins via the inheritMetadata plugin function. I generalized this approach so that it may be used for more data in the future, but right now it's only for chunks.

Additional context

I originally wanted to avoid the inheritMetadata plugin function by using configureServer, but this function isn't called for builds (where chunk metadata is primarily used). So I opted for going with a new plugin function, that's called from both build/server.

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What is the purpose of this pull request?

• [ ] Bug fix
• [x] New Feature
• [ ] Documentation update
• [ ] Other

Before submitting the PR, please make sure you do the following

• [x] Read the Contributing Guidelines, especially the Pull Request Guidelines.
• [x] Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• [x] Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• [ ] Update the corresponding documentation if needed.
• [ ] Ideally, include relevant tests that fail without this PR but pass with it.

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[milesj]

cc @yyx990803

[bluwy]

@milesj do you have any updates for this PR, and is it still needed?

[milesj]

@bluwy This problem will need to be addressed at some point when we integrate rolldown, but I'm not sure this approach is the best. We can close this for now.