Introduce GraphListener.ordinal method for sorting instantiated listeners

[dwnusbaum]

See jenkinsci/workflow-cps-plugin#1052 and jenkinsci/workflow-job-plugin#547.

Testing done

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 demonstrate the feature works or the issue is fixed

[dwnusbaum]

Unnecessary as of jenkinsci/workflow-cps-plugin@4241907 in jenkinsci/workflow-cps-plugin#1052.