Export Kubernetes event logs

[deliahu]

Requirements:

• output as json to stdout
• massage labels to match what is expected by Cortex
• Optional (or separate ticket): Add kubernetes event logs for the randomly chosen pod in cortex logs command

Possible tools:

• https://github.com/opsgenie/kubernetes-event-exporter (can be logged to stdout, not sure about structure)
• on GKE it ships with one by default (it has two containers: gke.gcr.io/event-exporter and gke.gcr.io/prometheus-to-sd, but that probably just can ship to stackdriver