ARIA roles no longer use DeprecatedFlyString, replace them with the
forwarding header, and StringView.h in one case, for other things from
AK used in those headers.
ARIA has its own spec and is not part of the DOM spec, which is what the
Web::DOM namespace is for (https://www.w3.org/TR/wai-aria-1.2/).
This allows us to stay closer to the spec with function names and don't
have to add the word "ARIA" to identifiers constantly - the namespace
now provides that clarity.
