Create Snippets::UpdateRepositoryStorageService

What does this MR do?

This MR creates the Snippets::UpdateRepositoryStorageService. This service will be used to move the snippet repository storage from one shard to another.

Most of its functionality comes from Projects::UpdateRepositoryStorageService. That's why we extracted most of the logic into a concern and then we reused it in both services.

Does this MR meet the acceptance criteria?

Conformity

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

Related to #218990 (closed)