- neighbour_config.conf file includes neighbour and measurement related parameters
Neighbour List:
 - nr_cellid: the identity of existing cell who has neighbour
 - neighbour_cell_configuration(list): includes the identity parameters
   of the neighbour cell such:
    - gNBID (incase of N2 Handover / to be identified from AMF)
    - nr_cell_id (target gNB needs to consider)
    - physical_cellId (needed for measurement reporting)
    - absoluteFrequencySSB (needed for measurement reporting)
    - subcarrierSpacing (needed for measurement reporting)
    - plmn / tracking area code (incase of N2 Handover / needed for AMF
      to identify / allow HO)

NR Measurement Configuration
 - Periodical
    - enable (default is 0, 1 enables the reporting)
    - includeBeamMeasurements, maxNrOfRS_IndexesToReport (configurable
      reporting parameters)
 - A2
    - enable (default is 0, 1 enables the reporting)
    - threshold , timeToTrigger (configurable reporting parameters)
 - A3
    - cell_id (the nr_cellid of neighbour cell. So this A3 parameters
      will be used for the neighbour
        - [-1] means default. so it can be applied to any neighbour if
          there is no specific config
        - Neighbour specific A3 Threshold can be used or default can be
          selected depending to the neighbour planning
        - The neighbour-config.conf specifies, apply default A3 for
          neighbours 3 and 4 | apply specific one for neighbour 2

    - offset, hysteresis, timeToTrigger (configurable reporting parameters)

the neighbour_config.conf can be included in the gNB.conf file. Example
is given: gnb.sa.band78.106prb.rfsim.neighbour.conf

A sequence array container is used for neighbour cell configuration. RRC
structure has this container.  A Measurement configuration structure is
defined. This structure has Periodical / A2 Event structures and also a
sequence container for A3 Event List.

These structures are filled during the initialization. While F1 Setup
Response is coming from DU to CU, the intra frequency / inter frequency
neighbour decision is given for the existing cell. Also new neighbours
could be added here if needed.