FD adapter for RFsimulator

A small FD adapter library for RFSimulator to be used for O-DU testing.

An example of how this can be used:

Start the core:

cd doc/tutorial_resources/oai-cn5g
docker compose up

Start gNB:

 sudo ./nr-softmodem -O ../../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band77.106prb.fhi72.4x4-fd-rfsim.conf --rfsimulator.serveraddr server --gNBs.[0].min_rxtxtime 4 

Start nrUE:

 sudo ./nr-uesoftmodem -C 4049760000 -r 106 --numerology 1 --ssb 516  --band 77 --rfsim --uicc0.imsi 001010000000001 

ping:

in oai-ext-dn container:

ping -I eth0 10.0.0.2 -s 20000

on host:

ping -I oaitun_ue1 10.0.0.1 -s 20000

iperf:

in oai-ext-dn container

iperf3 -c 10.0.0.2 -B 192.168.70.135

on host:

iperf3 -s -B 10.0.0.2