Extract ProjectRepositoryStorageMove logic into concern

What does this MR do?

In this we plan to implement the repository move logic for snippets. In #218992 (closed) we plan to implement the class SnippetRepositoryStorageMove similar to the existent ProjectRepositoryStorageMove. But, before that, we need to extract the logic in ProjectRepositoryStorageMove to a concern, in order to reuse it later in similar classes.

This MR does that, creating a new concern that it can be reused later. We also create some specs shared examples with the specs in ProjectRepositoryStorageMove in order to reuse them later with the new classes.

Does this MR meet the acceptance criteria?

Conformity

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

Related to #218992 (closed)