[WIP] PR: Add initial tests for remote client

[hlouzada]

Description of Changes

• Wrote at least one-line docstrings (for any new functions)
• Added unit test(s) covering the changes (if testable)

• Included a screenshot or animation (if affecting the UI, see Licecap)

Add fixtures to start an ssh server docker, start the remote client and ipythonconsole plugins, and register the remote server to be used.
Add plugin's tests with start/stop/restart kernels;
Add ipythonconsole test to start/stop/restart/kill kernels;

Affirmation

By submitting this Pull Request or typing my (user)name below,
I affirm the Developer Certificate of Origin
with respect to all commits and content included in this PR,
and understand I am releasing the same under Spyder's MIT (Expat) license.

I certify the above statement is true and correct: @hlouzada