Write test for accname edge case: datalist sub options

[cookiecrook]

Found out tonight suboptions in datalists have some broken label representations. Tracking here as an edge case test after the general accname automated testing is complete.

https://a11ysupport.io/tests/html/html/datalist.html
https://twitter.com/pauljadam/status/1641450665020116993

Thanks @weboverhauls for the heads-up.

[cookiecrook]

https://webkit.org/b/254967

[cookiecrook]

Probably blocked by web-platform-tests/wpt#39617 for the same reason optgroup is.

[cookiecrook]

If anyone wants to work on this good first issue, I think the test could go in either:

• /accname/name/comp_host_language_label.html
• or if you get a crash due to WPT test harness crashes if test receives "unknown error" from WebDriver  wpt#39617, then this could go in: /html-aam/fragile with the area and optgroup tests

[cookiecrook]

@zcorpan reminded us in the meeting this may be tricky since the datalist is not rendered, the label test may not be able to get at the rendered element directly... if not, a tree dump or other test may be required.