Stack area and bar series independently of each other

[flash1293]

Is your feature request related to a problem? Please describe.
Right now it's possible to end up with area and bar series which are stacked on top of each other.

Describe the solution you'd like
elastic-charts should handle this case by stacking the area and bar series independently of each other

Describe alternatives you've considered
This can be handled as part of the spec as well, but as this configuration is considered bad practice, it shouldn't be possible to configure it in the first place.

Additional context

Kibana Cross Issues
elastic/kibana#126586

Checklist

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[nickofthyme]

I don't think this is something that should be fixed on the elastic charts side.

The solution here would be to group all the bars/areas and split them into their own group using groupId to define separate Axis specs. Doing this in elastic charts would require us to assume the preference of the user if they want multiple axes or to ignore the defined stackAccessor, either is a bold assumption.

The task of splitting the specs to separate axes can be difficult if you want the separated axes to share the same domain extents. I opened #2519 to track this request.

[markov00]

I think we probably need to reconsider this. definitely Lens should block this behaviour, but we should also not provide an option for that.