Change all Package Registry related links

What does this MR do?

In !16770 (merged), we consolidated all Package Registry related docs under the same roof. This MR changes the links in the app itself.

Original issue: #29146 (closed)

1. Merge the docs first !16770 (merged)
2. Merge this MR

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content