UdpDriverCapability capability allows the holder to use two functions
only allowed by the UDP driver. The first is the
in udp_send.rs, which does not require being bound to a single port, since
the driver manages port bindings for apps on its own. The second is the
set_user_ports() function in
udp_port_table.rs, which gives the UDP port
table a reference to the UDP driver so that it can check which ports have
been bound by apps.