Notification emails for Auto DevOps

As we look to enable DevOps automatically, it's apparent that notification emails might become the first point of contact people have with CI/CD pipelines. We should improve them so that they are more functional and highlight more Auto DevOps functionality.

• Notify on first build of each branch (successful or not)
• Notify on branch repair (first successful pipeline after failure(s))
• Code Quality report in notification emails: https://gitlab.com/gitlab-org/gitlab-ee/issues/3058
• Review App in notification emails
• Code coverage in notification emails: https://gitlab.com/gitlab-org/gitlab-ce/issues/25602
• Include something special in notification emails for failures (or even successes) on implied CI: https://gitlab.com/gitlab-org/gitlab-ce/issues/35791

Related: https://gitlab.com/gitlab-org/gitlab-ce/issues/32638