New registration workflow

[cchaudier]

See upstream #331

Doing only for Unix

• [ ] create new new runner registration workflow vars with false by default
• [ ] print deprecated runner registration workflow if vars is set to false with link to https://docs.gitlab.com/ee/ci/runners/new_creation_workflow.html#the-new-runner-registration-workflow

  if vars is set tu true

• [ ] use ansible gitlab_runner_module to create runner
• [ ] register runner with --registration-token
• [ ] register runner with --token for new workflow only

[Miracle05]

#337 Is what you need