Show error when namespace/svc account missing

What does this MR do?

This MR ensures that an error is showed on the job page when a namespace/svc is missing.

What are the relevant issue numbers?

Closes #54506 (closed)

Preview

Simulate a failure

To simulate a failure:

1. Comment out this line.
2. Set up a fresh project and GKE cluster.
3. Run an auto-devops pipeline.
4. The pipeline should fail on the production step with the correct message.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• 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

TODO Frontend

• Add unit tests.
• Add a component for the unmet_prerequisites error.
• Add correct illustration.
• Add a More information link to the error message.

TODO Backend

• Add status for builds with failed prerequisites.