Geo - Remove code duplication on file registry finders

What does this MR do?

With the removal of the last feature flag in #222494 (closed) we can refactor the Geo::FileRegistryFinder, Geo::AttachmentRegistryFinder, Geo::LfsObjectRegistryFinder, and Geo::JobArtifactRegistry to remove the code duplication.

Screenshots

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.

Related issues

Closes #225841 (closed)