fix: rename serde for Self_ to "self" for direct deserialization of JSON

[lthiery]

Summary

This renames the serde of the Self_ field to be self. This allows the structs to be directly deserialized from JSON.

Checklist

• ran cargo make fmt
• using conventional commits to hightlight user-facing fixes and features

[augustoccesar]

Changes to files under the generated folder would be overwritten next time that the schema is updated.
There is a PR already to do this change on the codegen that will solve this issue (#490).

[arlyon]

Closing in favour of #490 which is merged now.

[lthiery]

Oh great, thanks! And thanks for pointing out the other PR - good to understand a little better how the codegen works.