Enabled the Lustre CSI driver by default in gke-a3-ultra blueprint and added commented out code with instructions to support managed lustre.

Manual testing steps performed:

1. Deployed the GKE A3 Ultra cluster with Managed-Lustre enabled.
2. Checked if the PVC is bound to the PV: kubectl get pvc
3. Mounted the PVC in a pod, which will mount the Managed-Lustre file system.
4. Checked if the pod is running and the volume is mounted: kubectl get pod
5. Wait for the pod to be in the 'Running' state
6. Exec into the pod: kubectl exec -it -- /bin/sh
7. Inside the pod, checked the mount:
8. df -h /mnt/lustre
9. mount | grep lustre
10. Managed-Lustre file system was mounted at /mnt/lustre and was able to read/write data to this path from within the container.

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