The e2e core framework and subpackages of e2e framework are defined.
The subpackages can import the core framework, but the core framework
should not import the subpackages. We've defined this dependency rule
after circular depencency issue happened.
This adds TODOs to understand what we should in this rule.
The framework/ssh.go code was heavily used throughout the framework
and could be useful elsewhere but reusing those methods requires
importing all of the framework.
Extracting these methods to their own package for reuse.
Only a few methods had to be copied into this package from the
rest of the framework to avoid an import cycle.
