Collect kube_pod_status_ready_time from KSM for kubernetes.state_pod metriscet

[MichaelKatsoulis]

Kube-state-metrics reports kube_pod_status_ready_time metric:

kube_pod_status_ready_time{namespace="kube-system",pod="kube-apiserver-kind-control-plane",uid="8cb4d4e1-b8b3-4bab-adc2-3e9d3687724c"} 1.698675692e+09

This metric indicates how long it took for a pod to become ready. In kubernetes state_pod metricset, we are currently collecting it.
It is a useful metric for Elastic's serverless platform for monitoring how long it took for applications to start.

[botelastic]

This issue doesn't have a Team:<team> label.

[elasticmachine]

Pinging @elastic/obs-ds-hosted-services (Team:obs-ds-hosted-services)

[mduarte]

I was actually thinking that perhaps we could also get other time metrics since they could be used to monitor other issues and alert on them.

e.g.

kube_pod_start_time
kube_pod_completion_time
kube_pod_status_ready_time
kube_pod_status_scheduled_time