optionally skip `post Setup operator environment`

The post Setup operator environment cleanup happens after all meaningful work is complete and immediately before stopping the workflow. Is cleanup necessary? At least in some cases, like when creating a ephemeral microk8s cluster for testing, couldn't we skip this step and leave microk8s running on the runner (for github to trash themselves)?

There might be cases where cleanup is important (if we bootstrap on an existing cloud?), but for microk8s I think it is unnecessary. It also takes maybe 2 minutes per run, which is a good portion of many integration tests.

charmed-kubernetes / actions-operator

optionally skip `post Setup operator environment` #20