Refine content and appearance of the project 'Configure' screen

[janfaracik]

Relates to jenkinsci/jenkins#9734.

Key changes

• The 'Build Triggers' section has been updated to feature the same content changes as core, it's now just 'Triggers' and there is now a description
• Pipeline section has been moved above 'Advanced' and a description has been added
• 'Quiet period' has been moved to 'Advanced', consistent with core

In Jenkins 2.491

In Jenkins 2.479.1 (no regressions)

Testing done

• Works as before

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue