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.