[OneDiscover] Histogram log.level color indication

[kertal]

📓 Summary

[!IMPORTANT]

• It's already doable in DataViewMode
• In ES|QL more it depends on https://github.com/elastic/kibana/issues/186369

When log.level is selected as a breakdown field, Discover's histogram should be displayed in a mode that is optimized for the consumption of log levels, which means it should be easy to detect log levels of critical, error, warning severity by applying term mapping to colors (tbd) and Breakdown: Filters, here's an example how it looks like in lens, and this is configureable in the Lens embeddable Discover:

Color mapping:

Breakdown:

TBD:

• which colors to use
• which terms to use for the Filter (e.g. error, err, critical, critical, warn, warning)

✔️ Acceptance criteria

• Extend UnifiedHistogram so it's Breakdown can be switched to Filters , that can be configured
• Extend UnifiedHistogram to allow colors by term mapping
• Make use of this enhancement to show the following terms with matching colors in the histogram when log.level is selected as Breakdown field:
  • critical
  • error
  • warning
  • info
  • debug
  • Other log levels
• Make use of this enhancement in the Logs Contextual Presentation

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[kertal]

Currently blocked by https://github.com/elastic/kibana/issues/191988