GCP XPN is in tech preview. There are two features which are affected:
1. selecting a DNS zone from a different project should only be allowed if tech preview is enabled in the install config. (Using a DNS zone from a different project will fail to install due to outstanding work in the cluster ingress operator). 
2. GCP XPN passes through the installer host service account for control plane nodes. This should only happen if XPN (networkProjectID) is enabled. It should not happen during normal installs.

4.12

For install config fields:
1.specify a project ID for a DNS zone without featureSet: TechPreviewNoUpgrade
2.run openshift-install create manifests
====
For service accounts:
1. perform normal (not XPN) install
2. Check service account on control plane VM

For install config fields: you can specify project id without an error
For service accounts: the control plane vm will have same service account used for install

For install config fields: installer should complain that tech preview is not enabled
For service accounts: should have a new service account, created during install