Test against well-known clients

[ewxrjk]

Description

Periodically we run into issues with well known clients, e.g. Paramiko or OpenSSH.
In order to get earlier site of these (and identify configurations that support them, prevent regressions) it should be possible to routinely test against them.

Analysis

My expectation is that this will be a set of docker containers used to run tests against various clients (and probably various platforms).