Extract the code to get the field name.

Extract the code to get the field name.

Ideally we can share this across searches (@monishdeb is hitting some things in case search that are solved
in contribution search so trying to cleanup these bits  - this just pulls out one small piece.

Once this is passing tests (which could be affected by my new deprecations
I think the other fields - fieldspec & 'qillname' if still required can get the same treatment.
in the next step.

Getting the fieldSpec & adding the qill is what I specifically want to genericise.