Inline neighbour cell arrays into the RRC neighbour configuration and
update RRC/DU helpers to use const-aware access and shared iteration
helpers when walking neighbour lists and building measurement configs.
Changes:
- Change neighbour_cells in neighbour_cell_configuration_t from a
seq_arr_t * to an embedded seq_arr_t field.
- Initialize and populate the embedded neighbour_cells directly in
parse_neighbour_cells_list in gnb_config.c, dropping dynamic
allocation of the neighbour list container.
- Refactor get_neighbour_cell_by_pci and nr_rrc_get_measconfig in
rrc_gNB.c to access the embedded neighbour_cells via const pointers,
introduce a local meas_cfg and a3_event_list, and iterate neighbour
cells with FOR_EACH_SEQ_ARR.
- Treat neighbour cell configuration entries as const in rrc_gNB_du.c
(get_cell_neighbour_list, label_intra_frequency_neighbours,
valid_du_in_neighbour_configs) and iterate neighbour lists with
FOR_EACH_SEQ_ARR instead of index-based loops.