CAPI support in upstream autoscaler

[hardikdr]

Improvement

ClusterAPI provider support in upstream autoscaler is going towards merging now. If I understand it well, it uses the unstructured types and dynamic informers, there seems to be a possibility we can directly consume it with MCM. Needs further investigation.

Refer: kubernetes#1866

[frobware]

I think the things you would want to be able to override or control at runtime are:

• API version
• Whether you want to support MachineSets
• Whether you want to support MachineDeployments, or both ^^

And the names of various annotations/constants:

const (
	machineDeleteAnnotationKey = "cluster.k8s.io/delete-machine"
	machineAnnotationKey       = "cluster.k8s.io/machine"

const (
	// GPULabel is the label added to nodes with GPU resource.
	GPULabel = "cluster-api/accelerator"
)

const (
	nodeGroupMinSizeAnnotationKey = "cluster.k8s.io/cluster-api-autoscaler-node-group-min-size"
	nodeGroupMaxSizeAnnotationKey = "cluster.k8s.io/cluster-api-autoscaler-node-group-max-size"
)