UdpDriverCapability capability allows the holder to use
two functions only allowed by the UDP driver.
driver_send_to() function 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
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.