Create worker to handle group repository storage moves

What does this MR do?

In this MR the worker that will handle group repository moves is introduced.

The logic is very similar to projects and snippets:

• https://gitlab.com/gitlab-org/gitlab/blob/master/app/workers/project_update_repository_storage_worker.rb#L1
• https://gitlab.com/gitlab-org/gitlab/blob/master/app/workers/snippet_update_repository_storage_worker.rb#L1

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Merge request performance guidelines
• Style guides
• Separation of EE specific content

Related to #299059 (closed) and #299058 (closed)