[Lens] Color non-numeric metrics using color mapping

[markov00]

Describe the feature:
Currently Lens Metric can apply a color by value only to numeric metrics.
With the addition of #137756 also strings, IP etc can now be used and represented as the metric value.
The request here is to provide the color mapping capability to all non-numeric fields.

Describe a specific use case for the feature:
If you have for example a boolean value that represents an on/off status, it will be great to represent and enhance the visualization with semantic colors (e.g. red off, green on).

related/similar to #168999

[elasticmachine]

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