Update go versions

This MR is the final little bit before we release v3 of client-go.

It adds the release notes around how to import and use the config package, in addition to performing the actual go update.

I plan to add the config/v3.0.0 tag manually once we merge release-client-3.0 into main. We change the config page infrequently enough that I think manually releasing it for now is fine.