review: new libraries and APIs that could simplify and improve iago (or hotstuff's use of iago)

- [gliderlabs/ssh](https://pkg.go.dev/github.com/gliderlabs/ssh#section-readme)
- [x/crypto/ssh](https://pkg.go.dev/golang.org/x/crypto/ssh)
- [ohgossh](https://github.com/artheus/ohgossh)
- [kevinburke/ssh_config](https://github.com/kevinburke/ssh_config) - currently used; check for updates.
