Add CanMoveRepositoryStorage concern to Group

What does this MR do?

In this MR, we add the necessary functionality to groups to interact with the repository_read_only column.

Groups don't have the column in its table but in the namespace_settings one. That's why we need to override some methods and use them as proxy for this operation.

This same concern has been added to Project and Snippet.

Epic &5166 (closed) Refs #299056 (closed)

Does this MR meet the acceptance criteria?

Conformity

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