Figure out a v2 strategy

[displague]

Several API changes have been to the backing API and the Go SDK. Some fields are persisting in the SDK, and are (in some cases) no longer provided by the API. Some SDK structures would benefit from refactoring.

Because this client is a semver v1 client, our breaking changes will need to be released with consideration of Go Module v2 semantics:
https://go.dev/doc/modules/release-workflow#breaking
https://go.dev/blog/module-compatibility
https://codeengineered.com/blog/2019/go-mod-major-versions/

https://github.com/equinix/ne-go#purpose should define the deprecation patterns used and the versioning strategy.

Once ready - we should publish a v2 with the deprecated fields removed.

This was previously discussed in #4 (comment)