Geo: Implement backfill of PackageFiles/Blobs

What does this MR do?

This is a part of the work needed to implement the backfill of PackageFiles. It does not include the change in RegistryConsistencyWorker class, it will be implemented in a separate issue/MR. We don't need a changelog item here!

Also, the documentation part will be in a separate MR

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required) Mike K: Docs will be updated in a follow up MR. I modified this description to not close the issue.
• 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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Part of #213872 (closed)