Create Empty States for Deployment Details Page

What does this MR do and why?

This MR adds empty states for the deployment approvals feature. It is available on the deployment details page. We use different versions of the empty state for CE and EE Premium.

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.

Screenshots or screen recordings

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

CE version	EE Premium version

How to set up and validate locally

1. Create a project and add the following .gitlab-ci.yaml file

   stages:
       - deploy
   image: alpine:latest
   
   deploy-prod:
       stage: deploy
       script:
           - sleep 10
           - echo "deploying prod"
       environment:
           name: production
           url: postgres://example.com
       when: manual
   
   deploy-staging:
       stage: deploy
       script:
           - echo "deploying staging"
       environment:
           name: staging
           url: https://example.com
       when: manual

2. Run the pipeline to create an environment and deployments.

3. Enable the feature flag deployment_details_page

4. Locate your deployment on Operate -> Environments -> Production

5. Click on the status badge to open the Deployment details page

6. Verify the empty states.

7. Simulate CE or a license under premium to verify the specific empty state for this case.

Review progress

• UX review
• backend developer review
• backend maintainer review
• frontend developer review
• frontend maintainer review

Related to #439413 (closed)