Adds scheduled and scheduledAt to CiJob

What does this MR do?

Adds scheduled and scheduledAt to CiJob

{
  project(fullPath: "gitlab-org/gitlab-shell"){
    pipeline(iid: "17"){
      stages{
        nodes{
          groups{
            nodes{
              jobs{
                nodes{
                  scheduledAt
                }
              }
            }
          }
        }
      }
    }
  }
}

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides

Related to #254236 (closed)