Allow setting machineNetwork CIDR in hcp CLI

[cwilkers]

In Baremetal (agent based) installs, it is necessary to define a machine network CIDR in addition to the clusterNetwork and serviceNetwork CIDRs. The HostedCluster CR supports this under spec.networking.machineNetwork but this is not an option for hcp create cluster agent

Currently, --cluster-cidr and --service-cidr exist as options, this issue proposes adding --machine-cidr for ipv4 and ipv6 CIDR entries.