Improve Metricbeat Kubernetes Volumes dashboard as currently it doesn't show useful information

[eedugon]

Describe the enhancement:

The main visualization in our [Metricbeat Kubernetes] Volumes default dashboard is not showing useful information, because the volume name is something generic and usually reused by a lot of pods. It could also mislead users.

For example this visualization is a bit meaningless as the names don't really identify much and actually belong to multiple pods:

Also, the metrics on datadir could be misleagind, as they are averages from a lot of real volumes belonging to different pods.

My proposal would be something like this, very similar, but including the pod names. As you can see the information is clearer.

I have included that visualization as part of a bigger dashboard here, in case you want to take a look.

Describe a specific use case for the enhancement or feature:

Kubernetes Monitoring with Metricbeat or Elastic Agent using the volume metricset.

cc: @gizas

[elasticmachine]

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