Allow customization of the OpenShift's internal domain

Reason-1: 

We are planning to have multiple clusters in our environment and same namespaces might exist in the clusters. We want to identifiy VM  clsuter name by using the DNS name. If cluster DNS is cluster.local for all clusters it will be very tough for us to identify the vm.
We tried using spec.subdomain to create unique DNS records per VirtualMachineInstance. < https://kubevirt.io/user-guide/virtual_machines/dns/ >. this makes the VM names very long <Service Name>.<Sub Domain>.<Namespace Name>.SVC.cluster.local
We cant use route or ingress as this will be SSH communcaition not HTTP. We are not using multus and total communication happens with Pod Network only. 

Reason-2:
We are using headless service to reach the VM within cluster and the name of the VM is very long in the format <Service Name>.<Namespace Name>.SVC.cluster.local. This will craete another problem for Infrastructure Operations team to identofy the VM in case of any operational or monitoring purposes as cluster.local is common for all clusers.