Better multiple axes identification with different domains

[nickofthyme]

Is your feature request related to a problem? Please describe.
Using multiple axes with different domains creates a scenario where the axis for the given element is not obvious.

Describe the solution you'd like
Some hover or possibly constant state to indicate which axis the data/element is relative to.

• Hover: Might blur the non-relevant axes, or inverse, hovering over axis shows only relevant elements.*
• Constant: Visible groupings or annotations to indicate axis. Or sorting left to right according the relative axis.

Screenshots

Related Issues
#759

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