Add support for sorting api packages list by created, relevance, popularity and top packages

https://pub.dev/api/packages?sort=updated is currently the only endpoint that works with the sort value.
The rest return the same data that you get when sorting updated.
### Missing support for:

- https://pub.dev/packages?sort=created // created: Packages are sorted by their created time.
- https://pub.dev/packages?sort=popularity // popularity: Packages are sorted by their popularity score.
- https://pub.dev/packages // Packages are sorted by the combination of their overall score and their specificity to the selected platform.
- https://pub.dev/packages?sort=top // Packages are sorted by the overall score.