Merge remote-tracking branch 'origin/e1ap-issue-878' into integration_2025_w04 (!3171)

- Refactor SCTP Association Response Handling
  - Unified function for both CU-CP and CU-UP handling
  - CU-CP: Notifies RRC of E1 connection loss with CU-UP
  - CU-UP: Initiates a new SCTP association request to regain E1 connection
  - this fix will prevent issue #878 from happening

- Send list of PDU Session Resources to Failed Setup in the (PDU Session
  Resource/Initial Context) Setup Response
  - depending on different failure scenarios
  - e.g. (#878) when No CU-UP is associated and still the CU-CP receives a PDU
    Session Setup Request
  - add relevant functions to handle NGAP Setup Response messages with failed
    list of items
  - this is an extra failure handling to make #878 is handled if it ever happens
    again

- NGAP Cause Refactoring
  - Refactor struct for NGAP cause group and value
  - Add extended radio network cause enumeration values
  - Refactor redundant code into a new NGAP cause encoding function

- Minor logging, function descriptions improvements

Closes #878

openair2/F1AP/f1ap_cu_task.c

@@ -65,7 +65,7 @@ static void cu_task_handle_sctp_association_ind(instance_t instance,
 static void cu_task_handle_sctp_association_resp(instance_t instance, sctp_new_association_resp_t *sctp_new_association_resp) {
   DevAssert(sctp_new_association_resp != NULL);
 
-  enum sctp_state_e state = sctp_new_association_resp->sctp_state;
+  sctp_state_e state = sctp_new_association_resp->sctp_state;
   if (state != SCTP_STATE_ESTABLISHED) {
     f1ap_cudu_inst_t *f1ap_cu_data = getCxt(instance);
     AssertFatal(f1ap_cu_data != NULL, "illegal state: SCTP shutdown for non-existing F1AP endpoint\n");