Configure longhorn persistence.defaultClassReplicaCount automaticaly based on nodes count

Summary

Specify in longhorn sylva-unit, persistence.defaultClassReplicaCount as a default value based on number of nodes (CP + MD) instead of leaving end-user specify it in his values.yaml (it is error prone)

Details

  longhorn:
    helmrelease_spec:
      values:
        persistence:
          defaultClassReplicaCount: <--

possible value is 1 or 3 depending the number of nodes (control planes + all nodes of machine deployments)

@cristian.manda @mohan.l.sharma