[Visualization] Mixing split series and split charts

[xlecluse]

Describe the feature:
When using "Visualize" it's actually not possible to display split charts with individual (and automatic) colors like a split series visualization (where charts are stacked).
It's not possible to have a common legend for split charts, like in split series

Describe a specific use case for the feature:
In a Kibana environment, this could be compared to a mix of split charts with split series display.

The use case is:
Showing the number of events that occured on each server in a 5min interval, on independant charts but with an only one legend and different colors associated to each chart/server.

This Feature request came from the Kibana forum, in the following topic :
https://discuss.elastic.co/t/mixing-split-series-and-split-charts-visualisation/152247
I have been told to open an enhancement request for this issue.

Thank you.

[elasticmachine]

Pinging @elastic/kibana-app

[stratoula]

This is related to #95556 (add a color dimension). We should take it under consideration when we start planning for small multiples in Lens