[cleanup/refactor] `cnudie` -> `ocm` + prepare for re-use in GitHubActions (minimise dependencies)

[ccwienk]

Context / Motivation

"CNUDIE" was renamed to OCM some years ago. Therefore, we should mv remaining code from cnudie package into ocm package. While doing so, dependencies, especially those against Concourse-Pipeline-Template / Gardener-CICD-Infrastructure should be reduced to allow for easier re-use, esp. from GitHub-Actions.

Implementation Notes

• caveat: consider usages from (need migration-path):

  • delivery-service
  • "lss"
  • "rbsc"
  • other non-public pipelines

• remove / replace usages of (at least downgrade to optional dependencies):

  • ci.util
  • ctx
  • dso.labels
  • ioutil (only required by cnudie.access, which can be moved to delivery-service entirely)

• make semantics of filters/filterfunctions consistent (similar to python's filter built-in: True -> keep value | False -> discard value)

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