Implementation of content-view publish and promote to selected  env

- Added a fn `add_remove_repos` to add/remove repo to/from selected content-view
- Added a fn `publish` to publish the selected content-view
- Added a fn `check_progress_bar_status` to see the publish/promote status. It is just to avoid the situation where publish is going on and UI start doing promotion.
- Added a fn `promote` to promote specific version to selected env.
- Added a test case `test_cv_end_2_end`

Please consider this as initial implementation of CV. As per the test case requirements, we can anytime modify these functions.