Add GPU/Accelerator support to VMs in GCPMachineTemplate

[jwmay2012]

What type of PR is this?

/kind feature

What this PR does / why we need it:
Adds the ability to configure Guest Accelerators like GPUs in a GCPMachineTemplate
Fixes #289

Special notes for your reviewer:
Tested and creates machines with GPUs correctly. After installing drivers and nvidia container runtime on the node, was able to get the GPU to run successfully in a Pod.
If you try to use an accelerator on the wrong instance type it will have an instance reconcile error from GCP that describes the improper API use.

OnHostMaintenance must be set to TERMINATE for GPU enabled machines.
https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/compute_instance#guest_accelerator
Confirmed this is correct. Instance reconcile is rejected by GCP otherwise.
I set this field automatically.

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

Add GPU/Accelerator support for VMs in GCPMachineTemplate

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: jwmay2012
Once this PR has been reviewed and has the lgtm label, please assign enxebre for approval. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

Hi @jwmay2012. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[netlify]

✅ Deploy Preview for kubernetes-sigs-cluster-api-gcp ready!

Name	Link
🔨 Latest commit	7b8e870
🔍 Latest deploy log	https://app.netlify.com/sites/kubernetes-sigs-cluster-api-gcp/deploys/671a6a29cf413100088f738b
😎 Deploy Preview	https://deploy-preview-1341--kubernetes-sigs-cluster-api-gcp.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[salasberryfin]

Thanks @jwmay2012

/ok-to-test

[richardcase]

@jwmay2012 - would you be able to run make lint on this change?