feat: Add terraform samples for GKE Attached clusters.

[hankfreund]

Description

Add samples demonstrating use of GKE attached clusters with both AKS and EKS. The samples:

1. create a cluster
2. prepare the cluster for attach
3. attach the cluster as a single Terraform apply step, which has been problematic for users.

[conventional-commit-lint-gcf]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot
https://conventionalcommits.org/

[hankfreund]

/gcbrun

[hankfreund]

/gcbrun

[Shabirmean]

@bharathkkb the CI tests are failing given some resource limitations. I think the tests run on the cloud foundation team's CI projects. Do you know who might be able to help Hank here?

Step #6 - "converge abm-gce-gpu":        
Step #6 - "converge abm-gce-gpu":        Error: Error waiting for instance to create: The zone 'projects/ci-abm-245d5a28-f04d/zones/us-central1-a' does not have enough resources available to fulfill the request.  '(resource type:compute)'.
Step #6 - "converge abm-gce-gpu":        
Step #6 - "converge abm-gce-gpu":        
Step #6 - "converge abm-gce-gpu":        A n1-standard-8 VM instance with 1 nvidia-tesla-k80 accelerator(s) is currently unavailable in the us-central1-a zone. Consider trying your request in the us-central1-c zone(s), which currently has capacity to accommodate your request. Alternatively, you can try your request again with a different VM hardware configuration or at a later time. For more information, see the troubleshooting documentation.
Step #6 - "converge abm-gce-gpu":        
Step #6 - "converge abm-gce-gpu":        
Step #6 - "converge abm-gce-gpu":        Troubleshooting documentation
Step #6 - "converge abm-gce-gpu":        https://cloud.google.com/compute/docs/resource-error
Step #6 - "converge abm-gce-gpu":        
Step #6 - "converge abm-gce-gpu":        
Step #6 - "converge abm-gce-gpu":          with module.anthos_bm_gcp.module.admin_vm_hosts.module.compute_instance["cluster1-abm-ws0"].google_compute_instance_from_template.compute_instance[0],
Step #6 - "converge abm-gce-gpu":          on .terraform/modules/anthos_bm_gcp.admin_vm_hosts.compute_instance/modules/compute_instance/main.tf line 45, in resource "google_compute_instance_from_template" "compute_instance":
Step #6 - "converge abm-gce-gpu":          45: resource "google_compute_instance_from_template" "compute_instance" {
Step #6 - "converge abm-gce-gpu":        
Step #6 - "converge abm-gce-gpu":        
Step #6 - "converge abm-gce-gpu":        Error: Error waiting for instance to create: The zone 'projects/ci-abm-245d5a28-f04d/zones/us-central1-a' does not have enough resources available to fulfill the request.  '(resource type:compute)'.
Step #6 - "converge abm-gce-gpu":        
Step #6 - "converge abm-gce-gpu":        
Step #6 - "converge abm-gce-gpu":        A n1-standard-8 VM instance with 1 nvidia-tesla-k80 accelerator(s) is currently unavailable in the us-central1-a zone. Consider trying your request in the us-central1-c zone(s), which currently has capacity to accommodate your request. Alternatively, you can try your request again with a different VM hardware configuration or at a later time. For more information, see the troubleshooting documentation.
Step #6 - "converge abm-gce-gpu":        

[hankfreund]

/gcbrun

[bharathkkb]

@Shabirmean it looks like stockout rather than quota? I suggest retrying it in a bit to see if it helps. If not we can ignore the failure or disable the test to unblock PRs.

[bourgeoisor]

Re-ran the test and it passed?

[hankfreund]

Looks like it is passing again, which is great. @bourgeoisor, as a code owner, can you approve so I can merge?

[bourgeoisor]

Looks good from my end.