Merge branch 'NR_F1C_F1U_extensions' of https://gitlab.eurecom.fr/oai/openairinterface5g into NR_F1C_F1U_extensions

- Change some elements names inside create_tunnel structure so that they are more generic to capture both N3 and F1-U use cases

MR !1081 : Prb based channel estimation
-An option for using average channel estimates over 1 prb is introduced in DLSCH and ULSCH. 
This improved BLER performance for MCS 28 when prbs are allocated across DC.

MR !1231 : Nr msg3 retransmission
-Implement re-transmission of MSG3 gNB and UE
-Fixes content resolution timer at UE

MR !1236 : nr: add T trace for msg4 (rrc setup)

Merge branch 'develop' of https://gitlab.eurecom.fr/oai/openairinterface5g into NR_F1C_F1U_extensions

Merge branch 'NR_F1C_F1U_extensions' of https://gitlab.eurecom.fr/oai/openairinterface5g into NR_F1C_F1U_extensions

- Trigger SRB2 and DRB configuration and RRC->MAC configuration
- Remaining: gtp-u tunnel creation at the DU side, triggering and handling of UE context setup response

MR 1170 : 5G nFAPI Improvements
- Bugfixes in packing/unpacking
- Adds uplink indication functionality
- Changes the nFAPI system architecture to account for architecture changes in the develop branch
- Adds nFAPI system documentation
- Removes hardcodings

MR 1222 : Update RRC ASN1 file to version 16.4.1 

MR 1223 : Fixes to NR UE MAC PDU generation 
- included MAC CE sub-PDUs size in the computation of RLC data to transmit this fixes the error with residual mac pdu appearing at gNB side when transmitting higher amount of data 
-  got rid of the nr_generate_ulsch_pdu and moved the relevant UL-SCH MAC PDU generation procedure within the nr_ue_get_sdu and nr_ue_get_rach 
-  reduced memcpy calls and unnecessary memory allocations 
-  fetching RLC data and SDU size from the mac_rlc_data_req, removed the call to mac_rlc_get_buffer_occupancy_ind 
-  introduced a new function to generate the MAC CEs sub-PDUs 
-  removed unnecessary function input parameters 
-  minor fixes and cleanup 
-  enhanced logging

MR 1227 : removed duplicate structure, changed 'x' to 'r' and 'y' to 'i'