[New Feature]: Separate layer variables for FeatureID, mouseover, and onClick

Checked for duplicates

Yes - I've already checked

Alternatives considered

Yes - and alternatives don't suffice

Related problems

The "useKeyAsName" layer variable is used for mouseover events and for the Feature ID (unique value at top) in the Info tool. If that property is not meant as a Feature ID, e.g. it contains HTML, it becomes unusable for a Feature ID.

Describe the feature request

I'd like to have separate variables for Feature ID, mouseover, and feature
"onClick" events. Something like:
"useKeyAsName" = For Feature ID
"useKeyAsDisplay" = shows property(s) as a mouseover popup
"useKeyAsID" = uses this property as the unique Feature ID in the Info Tool.

Default option (i.e. no variables defined) works as always with the first feature property for all three events. For backward compatibility, "useKeyAsName" could be kept for mouseover events, but let the first feature property always be the first property in the file.

Start by locating useKeyAsName and its consumers for mouseover events, onClick behavior, and the Info Tool's Feature ID. Done means separate variables control those three uses while the default behavior and backward compatibility described in the issue remain intact.