We made the comment thread focusable and improved keyboard navigation in #71883

To prevent regressions in this feature improvement, let's add the following e2e test:

• When a comment thread is focused, screen readers should read an excerpt of the comment.
• The Enter key should open and close a focused comment.
• Pressing Esc in a comment thread should close the comment and focus it.
• Pressing the Resolve Comment button should close the comment and focus it.
• Pressing the Cancel button should close the comment and focus it.