Find a place to store the kubermatic cluster id

[nce]

We get the kubeconfig from there:
https://github.com/adorsys/ops-k8s-bootstrap/blob/18d81d1c391083587b9c85dd251a949840a94a05/.github/workflows/pr.yml#L41

The projectID (first cryptic string) is static, but the second id (reflecting clusterID) needs to be configured somewhere.

I've no idea where. These values could/should(?) be masked: https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#example-masking-a-string

AC:

• should be easily found/changed
• configured in only one place
• evaluated if this is a "private" information and better stored in Secretsmanager

[nce]

We used to have the clusterID outputted by terraform. This is not possible if the cluster is newly created and not present in the tfstate.

I've now moved to a static file which we just cat