We have to list the set of allowed values for the DOMTokenList to not
throw when asking if one is supported.
This fixes an issue where YouTube embeds would hang indefinitely trying
to report an endless series of exceptions, seen on https://null.com/
This allows us to disable test output, which performs expensive assert
tracking. This was making our imported tests run significantly slower
than tests run via `WPT.sh`.
Formatting the output ourselves also allows us to remove unnecessary
information from the test output.
This commit also rebaselines all existing imported WPT tests to follow
the new format.
This shouldn't just be a simple reflection of the label attribute.
It also needs fallback to the HTMLOptionElement.text property if the
label attribute is absent.
