This allows us to use standard Serenity IPC infrastructure rather than
manually creating FD-passing sockets. This also lets us use Serenity's
WebDriver Session class, removing the copy previously used in Ladybird.
This ensures any changes to Session in the future will be picked up by
Ladybird for free.
This adds a WebDriver binary for Ladybird to make use of Serenity's
WebDriver implementation. This has to use the same IPC socket handling
that was used to make WebContent work out-of-process. Besides that, we
are able to reuse almost everything from Serenity.
