QSL label query should allow for dashed keyname

Currently, it's not possible to structure a QSL query which is looking for keys in the @label property when those keys have a dash in them.

For example:

node[@labels.$k8s-app="hi"]{*} // causes API error
node[@labels.$app="hi"]{*} // does not cause API error

This need (to be able to look for key names with dashes) came up in discussion with Adobe in work session to get KAtlas deployed in their infra.