[One Discover] include additional fields for summary column

[LucaWintergerst]

We should make some changes to the fields for the summary column.

remove

cloud.instance.id 
orchestrator.namespace

In addition we need to implement some logic to have a fallback, selecting the first field with a value in descending order:

Add fallback mechanism to container.name

kubernetes.container.name => k8s.container.name => container.name 

Add fallback mechanism to host.name

kubernetes.node.name => k8s.node.name => host.name

Add fallback mechanism to cluster.name

orchestrator.cluster.name => k8s.cluster.name

Add new fields with fallbacks

kubernetes.namespace => (k8s.namespace.name)
kubernetes.pod.name => (k8s.pod.name)

// only one of these will be present in a single doc:
kubernetes.deployment.name => (k8s.deployment.name)
kubernetes.replicaset.name => (k8s.replicaset.name)
kubernetes.statefulset.name => (k8s.statefulset.name)
kubernetes.daemonset.name => (k8s.daemonset.name)
kubernetes.job.name => (k8s.job.name)
kubernetes.cronjob.name => (k8s.cronjob.name)

[elasticmachine]

Pinging @elastic/obs-ux-logs-team (Team:obs-ux-logs)