setErrorByName uses wrong path to link

Problem/Motivation

When I call $form_state->setErrorByName() and pass a simple field name as $name, Drupal is expected to generate an anchor link pointing to the corresponding form element.
However, some form elements do not expose an element ID matching the field name (e.g. edit-field-myfield). Instead, only the wrapper element has an ID (e.g. edit-field-myfield-wrapper).
setErrorByName() always attempts to link to edit-field-myfield, but never to edit-field-myfield-wrapper, which means that some of the generated error links are non‑functional.

Сause of the issue:

The setErrorByName() stores the error correctly. The non‑functional link is created by Inline Form Errors, which builds the anchor link from the form element's #id. For a field, the error points to the widget element (element ID edit-field-myfield), which is themed with field_multiple_value_form. That theme prints the field's child elements but never outputs that #id, so edit-field-myfield is not in the page. Only the wrapper element (edit-field-myfield-wrapper) is always printed.

Steps to reproduce

1. Turn on the Inline Form Errors module.
2. Add a required text field to a content type.
3. Submit the form without uploading a file.
4. Click the field link in the error summary at the top.
5. Nothing happens, because the link points to an ID that is not in the page.

Proposed resolution

Make the error link point to a form element that really exists on the page. A field widget's own #id is not printed in the HTML, so use the #id of the field wrapper element (the widget's parent), which is always printed.

Remaining tasks

• Review the MR.
• Run the tests.
• Add functional test (optional).
• Commit the fix.

User interface changes

Error summary links now point to a field that really exists, so clicking them moves focus to the field. Nothing looks different.

Introduced terminology

None.

API changes

None.

Data model changes

None.

Release notes snippet

Inline Form Errors now links each error in the summary to a form element that is really shown on the page. Before, errors on single-value field widgets could link to an ID that was never printed, so the link did nothing.