Note that the changes to IPv4Socket::create are unfortunately needed as
the return type of TCPSocket::create and IPv4Socket::create don't match.
- KResultOr<NonnullRefPtr<TcpSocket>>>
vs
- KResultOr<NonnullRefPtr<Socket>>>
To handle this we are forced to manually decompose the KResultOr<T> and
return the value() and error() separately.