Introduce separate gNB-CU-UP ID in configuration

3GPP has the concept of a gNB-CU-UP ID and a (separate) gNB ID (for gNB,
CU-CP). This commit introduces the gNB-CU-UP as a separate ID that has to be
set in the configuration file when running as a CU-UP. For the
CU/monolithic gNB, it is optional (but needs to be the same as the
gNB-ID if specified).

The CU-UP ID is necessary, as some entities, e.g., the e2 agent, need to
signal both IDs, e.g., to reconcile a CU-CP and (multiple) CU-UP(s)
belonging together.

executables/nr-cuup.c

@@ -130,7 +130,8 @@ int main(int argc, char **argv)
   AssertFatal(rc >= 0, "Create task for CUUP E1 failed\n");
   nr_pdcp_layer_init(true);
   cu_init_f1_ue_data(); // for CU-UP/CP mapping: we use the same
-  MessageDef *msg = RCconfig_NR_CU_E1(true);
+  E1_t e1type = UPtype;
+  MessageDef *msg = RCconfig_NR_CU_E1(&e1type);
   AssertFatal(msg != NULL, "Send init to task for E1AP UP failed\n");
   itti_send_msg_to_task(TASK_CUUP_E1, 0, msg);