[Vis_type_heatmap] Implementation with elastic-charts

[stratoula]

Describe the feature:
We want to create a new plugin vis_type_heatmap that will use the elastic-charts heatmap implementation.

It should offer the same features as vislib and for some minors, both implementations will exist.

• We need a new switch for Heatmaps to switch between the two implementations
• Functional tests needed for the new implementation
• We should check for heatmap related issues and close anything that is solved with the new implementation
• The old implementation uses JSON blob and doesn't have explicit params**. This need to change.
• Heatmap should work with the EUI palettes. The vislib one uses these:

Should we also support them on the new implementation or not? --> TBD

Update: Yes we should support them and it will be feasible when this PR will be merged #102636

Note: there are some features missing from elastic-charts elastic/elastic-charts#875

Make it the default

• Small multiples are supported
• Display xy titles

Other missing features

• Highlight cells that belong to the same range on hover (also consider it for Lens)
• Heatmap visualization does not show empty buckets with date histogram #100301

Not supported (unless we have user's feedback

• Color scale (is not working correctly in vislib)
• Rotate and overwrite color values
• We always scale to data bounds

[elasticmachine]

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

[elasticmachine]

Pinging @elastic/datavis (Feature:ElasticCharts)

[flash1293]

Implementation notes:

There is already a heatmap chart renderer used in Lens. To avoid redundant code, it should be reused for the visualize heatmap implementation. These are the steps that need to be taken:

• Move current heatmap renderer

  kibana/x-pack/plugins/lens/public/heatmap_visualization/chart_component.tsx

  Line 36 in 59d4223

  export const HeatmapComponent: FC<HeatmapRenderProps> = ({

  (and the lens_heatmap, lens_heatmap_legendConfig, lens_heatmap_grid expression functions

  kibana/x-pack/plugins/lens/public/heatmap_visualization/expression.tsx

  Lines 34 to 35 in 0793753

  	import { HeatmapChartReportable } from './chart_component';

  ) into charts_expressions plugin and use it from both Visualize and Lens.
• If necessary, extend the functions and renderer to capture all use cases of the Visualize heatmap
• Lens will pass a lens_multitable context to the render function while Visualize works with datatable contexts. Rewrite the functions and renderer to use datatable instead of lens_multitable

[stratoula]

This is closed on v8.1.0