The changes in this PR implement the integration of GKE managed lustre.

• An example blueprint (examples/gke-managed-lustre.yaml) is added with the integrated managed lustre module enabled.

• Corresponding changes in terraform modules are added to support managed lustre integration.

• Integration test with coverage of functionality for managed lustre support is added.

• Testing details:

1. Provisioned the GKE cluster with example blueprint: gke-managed-lustre.yaml. Deployment of cluster was successul.
2. Applied the kubernetes pod manifest with persistent volume claim for the managed lustre storage capacity. Pod was applied succesfully.
3. Ran file I/O operations on the managed lustre volume mount via the applied pod. The file I/O were working as expected.
4. Provisioned a separate cluster using the example blueprint to use the same Managed Lustre volume (Cluster was provisioned on same VPC as the first and lustre instance attributes were passed in the blueprint to use existing instance). The second cluster was also provisioned successfully referring the existing managed lustre instance.
5. Applied manifest in second cluster and did the file I/O operations via pod of this second cluster. The file I/O operations were working as expected.
6. Destroyed the clusters and verified the clean destruction of resources that were provisioned.
7. Integration test have good coverage of functionality. The tests provision cluster using example blueprint, applies the kubernetes manifest using a lightweight busybox image. File mount is validated as it should be managed lustre instance and not just any ephemeral storage directory created. File I/O operations are then performed and assertions are validated for read and write contents from the file.