Add horizontal pod autoscaler to helm chart

[josh-ferrell]

What this PR does / why we need it: This PR adds the ability to create a horizontal pod autoscaler via the metrics-server helm chart.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #1384

[josh-ferrell]

/test pull-metrics-server-test-e2e-ha

[josh-ferrell]

I'm re-running pull-metrics-server-test-e2e-ha but I'm pretty certain that's a flaky test as the diff shouldn't be related to the creation of the HPA

[josh-ferrell]

I had to manually comment out the delegated _authz metrics from the []string that gets diffed against and add

for i := 0; i < len(metrics); i++ {
	if metrics[i] == "apiserver_delegated_authz_request_duration_seconds" || metrics[i] == "apiserver_delegated_authz_request_total" {
		metrics = append(metrics[:i], metrics[i+1:]...)
		i--
	}
}

for e2e HA test to complete but I see this may be fixed in #1383

[stevehipwell]

@josh-ferrell I've commented on the issue.

[yangjunmyfm192085]

/retest

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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: josh-ferrell, yangjunmyfm192085
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[logicalhan]

/triage accepted
/retest
/assign @serathius

[logicalhan]

/assign @stevehipwell

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@k8s-triage-robot: Closed this PR.

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