[k8s] Add hpa metrics

[ChrsMark]

Area(s)

area:k8s

Is your change request related to a problem? Please describe.

Similar to #1637 and #1636.

Part of #1032.

Describe the solution you'd like

Currently the metrics the Collector emits are the following:

k8s.hpa.max_replicas
k8s.hpa.min_replicas
k8s.hpa.current_replicas
k8s.hpa.desired_replicas

We need to ensure consistency with #1637 and #1636.

Thus the following would be a suggestion:

k8s.hpa.max
k8s.hpa.min
k8s.hpa.current
k8s.hpa.desired

Or:

k8s.hpa.replicas.max
k8s.hpa.replicas.min
k8s.hpa.replicas.current
k8s.hpa.replicas.desired

Describe alternatives you've considered

No response

Additional context

No response