This will make it easier to support both string types at the same time
while we convert code, and tracking down remaining uses.
One big exception is Value::to_string() in LibJS, where the name is
dictated by the ToString AO.
Success responses are meant to be wrapped in a JSON object with a single
"value" key. Instead of doing this in both WebContent and WebDriver, do
it once in LibWeb.
This moves communication and route matching for WebDriver endpoints into
LibWeb. This is to reduce the amount of duplication required to create a
WebDriver implementation for Ladybird.
In doing so, this introduces some cleanup of WebDriver handling. Routes
are now a compile-time array, and matching a route is nearly free of
allocations (we still allocate a Vector for parsed parameters). This
implementation also makes heavier use of TRY semantics to propagate
errors into one handler.
