Draft: Refactor ProjectRepositoryStorageMove

What does this MR do?

We are currently working towards (&3393 (closed)) support the moving of a Snippet's repository storage.

Currently, the ProjectRepositoryStorageMove implements a lot of functionality that can be reused in this effort, so this MR refactors it out into a reusable concern, RepositoryStorageMoveable

Refs #218992 (closed)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done