fix(nuxt): use parser to treeshake client-only declarations

[huang-julien]

🔗 Linked issue

Resolve #18949

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 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)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Hi 👋 ,
Using a regex to treeshake a variable declaration of a component isn't enough. This PR will use the parser to treeshake variables declarations of components that are only called client-side.

Done:

• identifiers

To do :

• ObjectExpression
• AssignmentPattern
• ArrayPattern
• Don't remove if it is called in the setup
• Refactor to make the plugin more readable
• add test .client components slots treeshaking

📝 Checklist

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

[codesandbox]

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[huang-julien]

I think this PR should be ready now. Also the plugin is ... "a bit more readable". If there's anything to add, please let me know 🙂

[danielroe]

Thank you - this is a nice improvement ❤️