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.

ci-scripts/docker/Dockerfile.unittest.ubuntu

@@ -13,11 +13,12 @@ RUN apt-get update && \
     DEBIAN_FRONTEND=noninteractive apt-get upgrade --yes && \
     DEBIAN_FRONTEND=noninteractive apt-get install --yes \
         libgtest-dev \
-        libyaml-cpp-dev
+        libyaml-cpp-dev \
+        libzmq3-dev
 
 RUN rm -Rf /oai-ran
 WORKDIR /oai-ran
 COPY . .
 
 WORKDIR /oai-ran/build
-RUN cmake -GNinja -DENABLE_TESTS=ON -DCMAKE_BUILD_TYPE=Debug -DSANITIZE_ADDRESS=True .. && ninja tests
+RUN cmake -GNinja -DENABLE_TESTS=ON -DOAI_ZMQ=ON -DCMAKE_BUILD_TYPE=Debug -DSANITIZE_ADDRESS=True .. && ninja tests