Track "basic response" separately "hint text"

[ccanash]

Currently, Testers use their own judgement to identify what part of an AT response is a "hint" (and they disregard that text when rendering verdicts). In the interest of transparency, the app should allow them to explicitly designate which part of an AT response (if any) is a hint. This will require updates to the data model, the user interface, and the automation system (which may be able to report this distinction by running tests twice and comparing the differences). Those should be tracked with dedicated Tasks.

This feature was first conceptualized during the 2024-11-14 meeting of the ARIA-AT Community Group: https://www.w3.org/2024/11/14-aria-at-minutes.html