[JENKINS-73771] do not lose the formField in the response

[jtnord]

Implements a crude way to not lose the important part that is the form field.

This is a quick and dirty approach, a complete fix should also take into account the describable being bound as in a nested page like /manage/configure a field name may not even be unique or provide enough context due to localization.

However for now this makes the situation less bad without introducing debt.

See JENKINS-73771.

Testing done

Proposed changelog entries

• human-readable text

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