Add nox session workflow:check

[ArBridgeman]

Summary

Unlike the Nox session workflow:update, this will check to see if a workflow:update were done if there would be modifications needed or not. For now, this is useful for developers and not the CI (would be a blocker as we are missing parts), but a follow-up issue should be made to activate this in the checks.yml.

Have the diff calculated. If there is no diff, then update the workflow:generate to have a different message & not try to write out the file.