Protected packages: Display busy table with loading icon

What does this MR do and why?

• Displaying the state busy for table that shows package protection rules
• Showing the loading icon when table is busy
• In the MR !140008 (merged), we forgot to declare the busy state for the table

🛠 with ❤ at Siemens

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

MR Checklist (@gerardo-navarro)

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the javascript style guides
• Conforms to the database guides

Screenshots or screen recordings

The screenshot shows the loading state of the table. You can also watch the video.

https://www.loom.com/share/33190f79f31142f2891707ef3fec5a97

How to set up and validate locally

1. In rails console enable the experiment fully

Feature.enable(:packages_protected_packages)

2. Go to http://gdk.test:3000/flightjs/Flight/-/settings/packages_and_registries
3. For a short moment, you should see the loading icon inside the table
4. Create new package protection rules

5.times { |i| Packages::Protection::Rule.create(project: Project.find(7), package_name_pattern: "@flightjs/flight-package-#{i}", package_type: :npm, push_protected_up_to_access_level: :maintainer)

6. Reload the page http://gdk.test:3000/flightjs/Flight/-/settings/packages_and_registries
7. Again, you should see the loading icon inside the table for a short moment; afterwards you should see the created package protection rules

Related to #413641