testing with 2x2 and 4x4 with N310, small modifications in nr_ru_procedures and usrp_lib.cpp for multiple antennas

adding beamforming support to FAPI: MAC fills ssb_beam_id_list in ssb config. PHY uses this info to fill new beam_id field. This is further copied to RU and applied there. Nothing is tested so far.

This commit contains work done by Eurecom and by Benetel.

NR PHY should now be able to handle multiple PRACH occasions

added handling for N_TA_OFFSET computation and changed some use of FAPI configuration in RU (used ru->config instead of ru->gNB_list[0]->config)

added scheduling of PRACH RX procedures in gNB and RU entities. Initialization of prach sequences added to nr_init.c

Bugfix: 1. fix the initial memory allocation; 2. correct the generation of the prach signal according to specs

Testing of NR PDCCH/PDSCH with RRC Configuration. added RRC configuration to NR UE. Updates to UE DCI procedures (moved to MAC) and updates to FAPI interfaces for UE. nr_dlsim is functional, added profiling information for gNB TX.

This reverts commit a9e07dce.