k8s follow-up - Uniformise core config keys

[davidferlay]

Context

• Followup of k8s support which introduces container.runtime: kubernetes

Observed

• In config.yaml,
  • actions_naming config key is under launchrctl key
  • runtime is under container key

launchrctl:
  actions_naming:
    - search: ".roles."
      replace: "."
    - search: "_"
      replace: "-"
container:
  runtime: kubernetes

Expected

• All core config keys should be placed at same yaml level for consistency