`id_for_label` is blank for widgets with multiple inputs such as radios
and multiple checkboxes. Therefore , `help_text` for fields using these
widgets cannot currently be associated using `aria-describedby`.
`id_for_label` is being used as a guard to avoid incorrectly adding
`aria-describedby` to those widgets.
This change uses `auto_id` as the unique identified for the fields
`help_text`. A guard is added to avoid incorrectly adding
`aria-describedby` to inputs by checking the widget's `use_fieldset`
attribute. Fields rendered in a `<fieldset>` should have
`aria-describedby` added to the `<fieldset>` and not every `<input>`.
Backport of 292f1ea90f from main
7f0275d8cb