fix: respect bare imports in browser field of package.json

[zhenyasav]

Description

This helps vite respect bare package imports in browser fields of package.json. We (@wittjosiah) discovered this when trying to use sodium-universal in a vite app, which asks for this substitution of sodium-native:

  "browser": {
    "sodium-native": "sodium-javascript"
  },

Relevant code in vite seemed to be assuming all such browser values are relative paths and not bare imports

Additional context

We're not sure if we're breaking anything else, and this problem seems related to (but not covered by) the solution in #8709

Let us know how to make this better and we'll get it there, thank you for your time!

Grand merci, Vite team!

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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

[sapphi-red]

Thanks for the PR! Sorry for missing this PR.
Closing as #11219 is merged.