Refactor package factories

🔦 What does this MR do and why?

The package factories have been getting a bit disorganized with a few files in particular containing factories for multiple models. This MR refactors those factories separating individual factories to their own files, and into better structured directories. It also renames a few of them to use the plural model name (for example package_file.rb => package_files.rb, which is the common convention for factory files.

No code is changed, added, or removed. Everything is simply moved around a bit for easier navigation.

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Related: #239436 (closed)