2 ANT TX/RX for USRP, updates

CI: fix flexran-rtc build Xenial

See merge request oai/openairinterface5g!1007

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

MR991: Remove hack in LTE PDCP for noS1 mode  
- Removes a hack which was used when LTE PDCP was used for NR in noS1 mode

MR993: UL and DL fixes LDPC short codewords 
- Fix UL & DL LDPC decoding for short LDPC code, e.g. Z_c is not multiple of 8
- Fix DLSCH data transmission with multiple DMRS symbols per slot
- small TA fixes on OAI 5G NR UE
- Implemented CQI measurement at NR UE
- NR UE cleanup 

MR1000: doc: fix build directory in BASIC_SIM.md

MR960: 256 QAM demodulation routines  
- Added functions for demodulation of 256 QAM signals.
- Added a command line flag to enable mcs table entry in PDSCH-Config in RRC to use 2nd MCS table for PDSCH.
- Added an option for using 256 QAM mcs table in nr_dlsim.

MR989: Docker and Deployment improvements (CI)  
- Image generation for eNB --> template for configuration files and dedicated entrypoint in Ubuntu
- Docker-compose-based EPC deploy
- Traffic test fully validated using the `trf-gen` container
- Flexran-rtc support when deployed in a container (Not fully done for the X2 Handover part)
- Added docker-compose-based eNB deployment
- Retrieve logs for such eNB deploymnent 
- Functional and log  update of nsa fr1 test but valid for gNB terminate also (enhanced ping stats and gNB markers)

MR992: Fix data transmission in "do-ra" mode
- UL and DL Traffic works now in do-ra mode, but there are still some PUCCH issues remaining. These issues are harming the acknowledgement of DL packets, and thus leading to unnecessary retransmissions.
The relevant warnings at UE are:
`PUCCH Invalid pucch resource indicator: at line 1082 in function select_pucch_resource of file openair1/SCHED_NR_UE/pucch_uci_ue_nr.c`
and
`PUCCH Error for number of bits for acknowledgment : at line 909 in function get_downlink_ack of file openair1/SCHED_NR_UE/pucch_uci_ue_nr.c`
Note: UE needs rbconfig.raw and reconfig.raw files from the *currently* running gNB, as the C-RNTI is random and different for each run.

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

rfsimulator: do not show "gap in reception" messages if complete slots are skipped (e.g. NR DL: gNB transmission, UE reception)