Add a visual indicator that quiz question answers and possibly results clarifications exist on quiz attempt results

**Is your feature request related to a problem? Please describe.**
It's difficult for a student to know they can click on a question to see any result clarifications. There's no down arrow or otherwise.

**Describe the solution you'd like**
Some visual indicator that you can click on a question to see the submitted answer and possibly result clarification, and maybe an extra visual indicator when there is a result clarification present.

**Describe alternatives you've considered**
Add a CSS class to make it easier to style if there's a clarification available. Also users can already customize `templates/quiz/results-attempt-questions-list.php` to do so.