[Lens] Automatically suggest TSDB dimensions for a given TSDB metric

[dej611]

Describe the feature:

In TSDB every metric is associated to all other dimensions by default.

While this might be useful to understand what are available dimensions, the relationship between metric and relative dimensions (aka those who make sense for such metrics) is lost when queried via the field caps API.
This information is still preserved at document level, so there are alternative ways to access such information.

Describe a specific use case for the feature:

Once we get this kind of information we could propose meaningful dimensions when the user is configuring a breakdown of a metric in Lens.

Implementation ideas

A PoC could be built with a top_metric request for each metric to gether which associated dimensions have been defined in each ingested document.

[elasticmachine]

Pinging @elastic/kibana-visualizations (Team:Visualizations)