Cleanup and refactor initial gNB configuration This is follow-up on !3048 (merged). Major changes in this MR: - Add config functions to reduce redundant code repeated in multiple places in the file - Add macros to reduce redundant code in gNB configuration - Refactor RCconfig_NR_NG - Cleanup obsolete and commented out code - Refactor includes in executables/nr-gnb.c - Introduce platform type plmn_id_t for consistency across the stack: F1AP, NGAP can now use the same struct type - And other minor formatting