ssh_dialer_test.go should use mock Go SSH server instead of container

[matejvasek]

Description

The test right now requires Linux Containerization so test cannot be run on macOS.
It could run on Windows with Windows' containerization but that would require adding new Windows docker file,
and probably some more Windows specific code.

Proposed solution

Replace containerized SSH testing server with SSH server in Go.

This would be also useful for porting the code back to podman.

Additional context

See https://github.com/knative-sandbox/kn-plugin-func/blob/main/docker/docker_client_ssh_test.go#L62