[CI] Automatically clean up environments on `master` on success

Mitchell Nielsenrequested to merge
ci-cleanup-env-on-master into master

Follow-up to !211 (merged).

Automatically clean up environments on master on success.

This ensures that releases for master don't sit around for 4 days (the auto_stop_in period). If the jobs fail, however, we'll have that 4 day period to either debug the environments in the clusters or the maintainer can dismiss the failures and manually trigger the cleanup jobs.

Edited by Mitchell Nielsen

Merge request reports