ZhengzheYang: support creating private GKE Autopilot clusters

JobBuild
191
05-12 22:22
pull-kubetest2-build 1524877650307321856
pull-kubetest2-gke-up-down-multicluster 1524877650240212992
pull-kubetest2-gke-up-down-singlecluster 1524877650198269952
pull-kubetest2-verify 1524877650269573120