[nit] Make protocol errors more typed and idiomatic.

[zeonzip]

Small DX/QoL cleanup; make GURT protocol lib's errors (GurtError) more directly typed as more idiomatic in rust style and remove redundant methods for GurtError.

[vercel]

@zeonzip is attempting to deploy a commit to the facehh's projects Team on Vercel.

A member of the Team first needs to authorize it.

[zeonzip]

This pr would also fit in with the eventual pr for issue #108 by replacing e.g GurtError::crypto(CryptoError::SomeError) with GurtError::Crypto(CryptoError::someError).

[face-hh]

i believe this PR should also fix the breaking changes in gurtlib-reliant subprojects

[zeonzip]

believe this PR should also fix the breaking changes in gurtlib-reliant subprojects

I'll do that then, but to also ensure other 3rd party libraries gets a heads up, we could also keep the construction methods but mark them as deprecated.