Std implements PacketListener using the Go net package's ListenPacket func.

ConnPacketConn is the interface that's a superset of net.Conn and net.PacketConn.

PacketConn is like a net.PacketConn but uses the newer netip.AddrPort write/read methods.

PacketListener defines the ListenPacket method as implemented by net.ListenConfig, net.ListenPacket, and tstest/natlab.