ZMQ radio

This commit introduces ZMQ-based radio library. Each pair of RX/TX antennas is
represented by a ZMQ REQ/REP socket pair which streams continuous IQ samples
from radio start until stop.

Usage:
Simplest configuration is to connect OAI NR UE to OAI GNB with the same number
of antennas - by inverting the RX and TX channels in ZMQ radio configuration the
gNBs TX is mapped to UEs RX antennas and vice versa.

NOTICE

@@ -84,3 +84,11 @@ Nuand: https://github.com/Nuand/bladeRF/tree/master?tab=License-1-ov-file
 
 Credits for https://github.com/pothosware/SoapySDR
 Pothosware: BSL 1.0 License
+
+Credits for https://github.com/zeromq/libzmq
+ZeroMQ authors: Mozilla Public License Version 2.0
+
+Credits for source code:
+  - radio/zmq/zmq_imported.cpp
+  - radio/zmq/zmq_imported.h
+Software Radio Systems Limited: BSD-3-Clause-Open-MPI