Description of problem:

The APIVIP and IngressVIP are currently being used in agentClusterInstall.yaml and when more than one VIP is needed then InstallConfig overrides are used, see https://github.com/openshift/installer/blob/master/pkg/asset/agent/manifests/agentclusterinstall.go#L182-L206.

Since the singular VIPs are deprecated we should use APIVIPs/IngressVIPs in all cases and remove the use of the singular VIP.

These fields are also being removed from the assisted-service API, see https://github.com/openshift/assisted-service/pull/5501