feat(handlers): allow method suffix in handler file path

[huang-julien]

🔗 Linked issue

resolve nuxt/nuxt#14003

❓ 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

Enhance the server handlers.
Allow (if the method is not specified) to use the method suffix as the handler's route method

📝 Checklist

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

[pi0]

Thanks for this pull request @huang-julien (and sorry to check late!). I think we could directly add this to nuxt kit addServerHandler. Nitro automatically uses this suffix but only for discovered files. Seems too much magic to me for options. We can first try to do this on nuxt kit and and useful enough backport as nitro behavior. (and if we do, we can do the normalization in single place of src/config.ts).