Create group repository storage move bulk service and worker

What does this MR do?

In this MR we introduce the service and worker to perform group repository storage moves in bulk. It will be only used by the API.

This same code is used for projects and snippets:

• https://gitlab.com/gitlab-org/gitlab/blob/master/app/services/projects/schedule_bulk_repository_shard_moves_service.rb#L1
• https://gitlab.com/gitlab-org/gitlab/blob/master/app/services/snippets/schedule_bulk_repository_shard_moves_service.rb#L1
• https://gitlab.com/gitlab-org/gitlab/blob/master/app/workers/project_schedule_bulk_repository_shard_moves_worker.rb#L1
• https://gitlab.com/gitlab-org/gitlab/blob/master/app/workers/snippet_schedule_bulk_repository_shard_moves_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 #299062 (closed) and #299064 (closed)