✨ Start adding KubeadmControlPlane controller

[detiber]

What this PR does / why we need it:

Adds the stubbing for the KubeadmControlPlane controller

Related to: #1756

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: detiber

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 [detiber]

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

[detiber]

For testing I used the following yaml:

---
kind: AWSMachineTemplate
apiVersion: infrastructure.cluster.x-k8s.io/v1alpha3
metadata:
  name: kcp-infra-template
  namespace: default
spec:
  template:
    spec:
      instanceType: t3.large
      iamInstanceProfile: "nodes.cluster-api-provider-aws.sigs.k8s.io"
---
kind: KubeadmControlPlane
apiVersion: cluster.x-k8s.io/v1alpha3
metadata:
  name: kcp-1
  namespace: default
spec:
  infrastructureTemplate:
    name: kcp-infra-template
    namespace: default
  kubeadmConfigSpec:
    clusterConfiguration:
  version: v1.16.2

With this I was able to see the log lines indicating that the controller is not yet implemented.

[detiber]

/assign @ncdc

[ncdc]

Do you want this to get merged as-is (pending review), then do a follow-up for the real implementation?

[detiber]

Do you want this to get merged as-is (pending review), then do a follow-up for the real implementation?

I figured we could start with a stubbed out implementation and start building up the needed functionality iteratively.

I'm hoping to keep down the bandwidth needed for reviewing (and the breakage for testing) to a minimum as we work towards the full implementation.

[ncdc]

Great start! Nothing major in my comments. Mostly nits & some small questions.

[ncdc]

#1836 should fix the integration test flake

[randomvariable]

/retest

[detiber]

@ncdc @randomvariable this should be ready for another pass now.

[ncdc]

/lgtm