Rule 2ee8b8 ("Visible label is part of accessible name"): adding label text as part of visible label for labelable elements

[shunguoy]

Using label elements to associate text labels with form controls (e.g., radio, checkbox) is common, and may be required by WCAG. If a labeled element doesn't have a valid aria-label or aria-labelledby attribute, the text from the label element can be used as an accessible name. However, suppose a labeled element has an aria-label or aria-labelledby attribute. In that case, the accessible name is calculated from the aria-label or aria-labelledby, and this rule should be triggered (with an error) if the label text is not part of the accessible name.
For example,
email:

Also, refer to #2075 for more discussions.