[Lens] Support a "break down by" option for the Metric chart type

[wylieconlon]

Lens, Visualize, and TSVB all have a Metric chart type which shows a large number with a label. In comparison to the others, Lens is missing the "break down by" feature.

The layout of a metric with "break down by" should be a standard flexbox layout with overflow, exactly like the TSVB layout.

The main issue with this chart type is fitting the text sizes into the constraints of the container. We already have a custom implementation that uses the container sizing, so it should be possible to extend this container-based sizing to work with multiple metrics.

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[drewdaemon]

Addressed in the new metric visualization (#136567)! 🍾