Add rrc_gNB_send_NGAP_PDUSESSION_SETUP_RESP
Fix some problems about pdu session setup

Removed changes in fix_scc to avoid impact on the actual value of ssb_PositionsInBurst_Bitmap in the archived configuration files

MIB NR: pdcch_ConfigSIB1 selection and fill using the configuration file, and using a dynamic method.

This commit contains work done by Eurecom and by Benetel.

Modify kenb to kgnb
Modify some warnings

Modify kenb to kgnb
Modify some warnings

This commit introduces several enhancements in X2AP and RRC to deal
with ENDC. The main goal is to deal with UE's on/off and with various
errors.

The following work is included:

    - DC prep and DC overall X2 timers
    - X2 messages for UE release and DC timers' timeout

Open problems:

    - what to do when the UE sends an scg Failure? This commit removes
      the UE. And this removal may not be correctly done
    - UE removal in the gNB's PHY layer (a next commit is coming,
      but it is hackish and will need a rework)