Automatic merge from submit-queue

Make a vSphere cluster the failure_zone

vSphere cloud provider returns the FailureZone as Cluster, if the VM belongs to a ResourcePool under a Cluster. 

fixes: #30933

* Currently the vSphere cloud provider treats Datacenter as the failure
  Zone.  This doesn't necessarily work since in the current implemention
  Kubernetes nodes cannot span Datacenters.
* This change introduces Clusters as the failure zone, while treating
  Datacenters as Regions
* Also updated tests for Zones