improve the UIX promotions page

[Spyna]

In the GUI of the promotions page , there is no clear separation between the various promotions, and sometimes you may press the wrong one.

This PR adds a container to the various sections of the page, changing the style as seen in the images below

before

after

See JENKINS-72461.

Your checklist for this pull request

• Pull request title represents the changelog entry which will be used in Release Notes. JIRA issue is a part of the title (see existing PRs as examples)
• Please describe what you did. Short summary for reviewers. If the change involves WebUI, add screenshots
• Link to relevant Jenkins JIRA issues or pull requests
• Test automation, if relevant. We expect autotests for all new features or complex bugfixes
• Documentation if relevant (new features). We want to use Documentation-as-Code, just put docs to README or to new Doc files
• Javadoc for new APIs. Any public/protected method is considered as API unless annotated by Restricted (docs)

CC

@mention

[NotMyFault]

Thanks :)