[tools]implement openstack backend
|Target version:||QA - future|
- #12158: As a SLE product owner I want openQA to test SLE on openstack using openQA to ensure SLE works as expected within cloud environments
- #12160: As an openQA infrastructure manager I want to use openstack for worker nodes to have a more scalable openQA environment
- As an openstack product owner I want to see more testing of openstack to ensure it works in more applications (implicitly solved with #12158 and #12160)
With openstack backend, openQA will get broader hardware coverage, including real hardware.