Add the GCP technical demo views

Follow up of !139797 (merged)

🔭 Context

This adds the required views for the demo needs from #433514:

• One page to ask all the required parameters.
• One page to use those parameters to execute the service from !139797 (merged) and present the results.

⚠ These changes are for demo purpose only and will not be used outside the demo ⚠ As such, several shortcuts were used.

Additionally, these changes are gated behind:

• Executed on gitlab.com
• a feature flag: https://gitlab.com/gitlab-org/gitlab/-/issues/434685
• User with read_container_images on the target project.
• Project is private

🤔 What does this MR do and why?

• Adds two pages: setup and list docker images.
• Gate them behind the requirements listed above.
• Add the related specs.

Those changes are behind a feature flag.

🖼 Screenshots or screen recordings

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

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.