Upgrade go-eth2-client automation workflows

Update go-eth2-client automation workflows to have the following automations in place:

- [ ] Dependabot scans
- [ ] [Golang version autoupdater](https://github.com/attestantio/go-block-relay/blob/master/.github/workflows/update-go-version.yml)
- [ ] [Attestant Go Linter](https://github.com/attestantio/attgo-linter)