Improve navigation for Package features

What does this MR do?

This adds a Package top level item to the project navigation. In the EE version, the sub items will include both List (listing your packages) and Container Registry. In the CE version, only Container Registry is a sub item.

The navigation menu should also respect if either feature is turned on / off. The main Package top level link will change where it links to based on certain criteria:

• If Packages is enabled - will link to the Packages list page
• If Packages is disabled but Container Registry is enabled - will link to Container Registry
• If both Packages and Container Registry are disabled - nothing will display

CE backport can be found here: gitlab-ce!30256

Does this MR meet the acceptance criteria?

Screenshots

New Top Level

CE Version

EE Version

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

Performance 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

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

Closes #11639 (closed)