feat: config hmr support for routeRules and rutimeConfig

[pi0]

🔗 Linked issue

❓ 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 supports HMR config updates for runtimeConfig and routeRules objects for nitro dev to rebuild the app without full reload.

A manual hook nitro.updateConfig() is also exposed to update this configuration on demand programmatically (useful for integration with other frameworks like Nuxt)

📝 Checklist

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

[pi0]

Early merging to try and improve on edge channel