Modify package registry project settings section with feature flag

What does this MR do and why?

Updates project package registry settings components to render card layout based on feature flag.

Adds feature tests for packages protection rules

EE: true

Changelog is not required since these changes are under a feature flag.

Note: Since this MR is quite big already, changes are focused only on the Package registry section. Container registry section is being updated in Modify container registry project settings sect... (!175502 - merged).

References

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• Design: #500217[settings-expanded.png]
• We intend to update the dependency proxy settings separately as part of #503395 (closed)

MR acceptance checklist

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Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

With feature flag turned off	Before	Layout: No packages protection rules	Layout: Packages protection rules with pagination

How to set up and validate locally

1. To see the Dependency proxy section, run GDK in SAAS mode

2. (Optional) Setup container registry

3. Visit Project > Settings > Packages and registries.

4. In rails console enable the experiment fully

   Feature.enable(:reorganize_project_level_registry_settings)

5. Confirm that Package registry section looks like the one in screenshot & the settings are usable.

Related to #500217 (closed)