update NR MAC/RLC/PDCP stats

this MR enables to get stats of gNB from FlexRIC

content

• add more arguments in NR_mac_dir_stats_t and gNB_MAC_INST
• create the data structure for RLC and PDCP statistics data (nr_rlc_statistics_t and nr_pdcp_statistics_t)
• calculate the average waiting time for packet transmission in RLC

testing

• end to end test with USRP b210 and Quectel UE(RB500Q-GL) by using config targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf