-Upon reception of SgNB Addition Request from the eNB, the gNB configures pdcp and rlc entities for the list of DRBs provided from the eNB

-Create nr_rrc_rlc_config_asn1_req function
-Update RLC DRB addition functions with NR structures instead of LTE

-Create nr_rrc_pdcp_config_asn1_req function
-Update PDCP DRB addition functions with NR structures instead of LTE

- get preamble from rach_ConfigDedicated in contention free mode
- do preamble selection only in prach slot

Initially targeting ENDC setup with commercial UE
- Missing nr_rrc_pdcp and nr_rrc_rlc configuration wrt the established DRB
- Remaining to test with user plane data traffic (Downlink and Uplink)

ENDC S1-U gNB support: Separate some GTP functions between eNB and gNB. Downlink traffic from SGW arrives properly at gNB now after path switch

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