Add cluster autoscaler scale from 0 support

[davidspek]

User Story

When using the cluster autoscaler, one of the big advantages is that it is possible to add multiple sizes of node groups that can automatically scale as needed. The big downside to this is that a user must always run 1 node of each group if scaling from 0 isn't supported. There is an accepted proposal that Cluster API providers can choose to implement that would enable scale from 0 support.

https://github.com/kubernetes-sigs/cluster-api-provider-kubemark/pull/30/files

Detailed Description

The support for scale from 0 for the cluster-api provider is not yet implemented in the cluster autoscaler, progress for this is being tracked in this issue and a unmerged working version of the cluster autoscaler can be found in this comment.
However, it would be good to implement the needed support for scale from 0 in the cluster-api-provider-packet so that users can benefit from this feature as soon as it is released.

Along with the proposal, the changes in this PR can be used as a guide on how to implement scale from 0 support.

/kind feature

[davidspek]

@cprivitere You might also be interested in this. This along with kube-vip and metro are what I have on my list for the distribution I'm working on.

[elmiko]

@davidspek i have opened a PR for the autoscaler, kubernetes/autoscaler#4840

[k8s-triage-robot]

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/lifecycle stale

[k8s-triage-robot]

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages issues and PRs according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

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/lifecycle rotten

[elmiko]

fwiw, this feature has merged in the autoscaler

[davidspek]

@elmiko Awesome, thanks for the heads up.

[cprivitere]

/lifecycle frozen

[cprivitere]

/remove-lifecycle rotten