Minimal MachinePool support

[justinsb]

• Initial spike: GCPMachinePool

• GCPMachinePool: generated code/manifests

This continues the work started by @BrennenMM7 in #901 . I also combined in the support from cluster-api-provider-aws to see what we want to borrow from that, and will whittle the code we don't need from cluster-api-provider-aws away.

NONE

[netlify]

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

Name	Link
🔨 Latest commit	6449078
🔍 Latest deploy log	https://app.netlify.com/projects/kubernetes-sigs-cluster-api-gcp/deploys/68b1d09eb5dfa00008f91e52
😎 Deploy Preview	https://deploy-preview-1506--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 project configuration.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: justinsb

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

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [justinsb]

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

[justinsb]

This PR is WIP while I whittle down the unneeded code from cluster-api-provider-aws and generally make this reviewable. But I am uploading as this is a checkpoint that works (in a limited way!)

[justinsb]

Removing the WIP. I will still try to whittle down the code by extracting helpers etc, but it's already approaching the reviewable ballpark!

[justinsb]

So the linter is blowing up on the TODO comments. How do we want to track next steps in code? If we don't want to do // TODO because golangci, maybe we do // TASK?

[k8s-ci-robot]

@justinsb: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cluster-api-provider-gcp-apidiff	6449078	link	false	/test pull-cluster-api-provider-gcp-apidiff

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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. I understand the commands that are listed here.