fix(nuxt): transform #components imports into direct component imports

[antfu]

🔗 Linked issue

closes #20492 (as a better fix)

resolves #20439
resolves #20450
resolves #20449

❓ Type of change

• 📖 Documentation (updates to the documentation, readme or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

With #20259, it becomes more difficult for rollup to tree-shake out unused components, and side effects were persisting in the entry file. This change transforms imports from #components into individual imports of each component, meaning that there should be no possibility of side-effects from unused components.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

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[antfu]

/cc @danielroe do you remember what was componentNames introduced for? Should we keep supporting it?

[danielroe]

I think we introduced componentNames in nuxt/framework#4150, with the idea that it might be used by a preview mode/editor/overlay that needed to know what was available. Ideally we'd keep supporting it; it could be another virtual module that would be tree-shaken if not used.