Autogenerate attestation libraries using protoc

[adityasaky]

This PR adds a GitHub Actions workflow to regenerate libraries using protoc. The action is triggered once a week as well as when something is pushed to main.

(We need the scheduled run as protoc is configured to use version 3.x so we may have newer tooling even if there are no changes here for a week to main.)

[marcelamelara]

Thanks! Do we need to update the documentation in docs/protos.md to remove the explicit requirement to regenerate the language bindings manually?

[TomHennen]

Thank you!

Also, my apologies if my other questions are daft, I've never done GitHub Actions before.

Finally, did we have some other documentation that suggests people regenerate the libs when modifying the protos? I'd assume that would change now?

[adityasaky]

Also amended the protos doc to instruct contributors not to regenerate libraries.

[adityasaky]

Updated go_setup target in Makefile to be a go install of the Go generator. Also removed the explicit versioning so the one in go.mod is used by default.

[marcelamelara]

LGTM, thank you!