Is your feature request related to a problem? Please describe.
There is no any way to hide a series in legend and still render it in the chart

• show in legend
  

• hide in legend
  

Describe the solution you'd like
Add a prop to a series (e.x. hideInLegend) to hide the series in legend:
<LineSeries { ... } hideInLegend={series.hideInLegend} />

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

Kibana Cross Issues
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Checklist

• this request is checked against already exist requests
• every related Kibana issue is listed under Kibana Cross Issues list
• kibana cross issue tag is associated to the issue if any kibana cross issue is present