Add "kube_horizontalpodautoscaler_info" metric

[Serializator]

What this PR does / why we need it:
Adds a metric which exposes the scaleTargetRef.apiVersion, scaleTargetRef.kind and scaleTargetRef.name of the HorizontalPodAutoscaler resource objects in the cluster.

How does this change affect the cardinality of KSM:

Adding a new metric for the HPA target will have a slight impact on cardinality, but most clusters have at most a double or triple digit amount of HPAs. So we are talking about at most 1000 newly added time series, which is really not that significant compared to the number of time series we export for pods and nodes.

Which issue(s) this PR fixes:
Fixes #1635

[mrueg]

/approve

[fpetkovski]

/lgtm Nice work

[mrueg]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: fpetkovski, mrueg, Serializator

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