fix: Move error.rs to protobuf

[jonathanc-n]

cc @gabotechs

[gabotechs]

Thanks! just a small comment and we can move this into main

[gabotechs]

Note how in all the modules of the project, we try to be strict about what's visible to the outside by not making the inner modules public. It would be fine to be consistent here and:

• instead of blindly exposing the inner errors module:

Suggested change

	pub mod errors;
	mod errors;

• Just expose the few things that are strictly needed:

pub(crate) use errors::{
    datafusion_error_to_tonic_status, map_flight_to_datafusion_error,
    map_status_to_datafusion_error,
};

[jonathanc-n]

Yes this makes sense. I like the way this is done compared to Datafusion, lets you see everything that is public at a glance 😄

[gabotechs]

Nice! as soon as pipelines are green I'll merge this