feature: support for generic text in OSv3.yml

[ioggstream]

The extra_openshift_ansible_params requires valid json, while we could easily add yaml configuration and comments to our files, eg.

All the issues (syntax, override,...) that are still present with extra_openshift_ansible_params apply.

ose_extra_vars: |
  # This parameter supports a readable yaml
  debug_level: 4
  # And I can motivate variables assignment.
  #   don't schedule container on infra nodes
  osm_default_node_selector: region=primary