Refactor RRC->MAC Communication: Replace ITTI with notifiedFIFO for Multi-UE Support

- Replaced ITTI message queues with notifiedFIFO for RRC to MAC communication in UE.
- Enables correct message delivery to multiple MAC instances running in parallel threads.
- Introduced `nr_mac_rrc_message_t` union for MAC-RRC messages.
- Updated all relevant message handling and initialization code to use notifiedFIFO.

executables/nr-uesoftmodem.c

@@ -500,12 +500,14 @@ int main(int argc, char **argv)
                                     get_softmodem_params()->numerology,
                                     nr_band);
         } else {
-	  MessageDef *msg = NULL;
-	  do {
-	    itti_poll_msg(TASK_MAC_UE, &msg);
-	    if (msg)
-	      process_msg_rcc_to_mac(msg);
-	  } while (msg);
+          do {
+            notifiedFIFO_elt_t *elt = pollNotifiedFIFO(&mac->input_nf);
+            if (!elt) {
+              break;
+            }
+            process_msg_rcc_to_mac(NotifiedFifoData(elt), inst);
+            delNotifiedFIFO_elt(elt);
+          } while (true);
           fapi_nr_config_request_t *nrUE_config = &UE[CC_id]->nrUE_config;
           nr_init_frame_parms_ue(&UE[CC_id]->frame_parms, nrUE_config, mac->nr_band);
         }