feat: allow disabling payload extraction

[pi0]

🔗 Linked issue

resolvesnuxt/nuxt#14931

❓ 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

This PR allows disabling payload extraction with nuxi generate introduced in RC.10 (#6455) using experimental.payloadExtraction: false

exportdefaultdefineNuxtConfig({experimental: {payloadExtraction: false}})

Remarks:

• Even by disabling the (static) payload extraction, /_payload.js endpoint is still available for renderer. It is a separate feature
• I've confirmed tree-shaking keeps working with refactors

📝 Checklist

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

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