Merge remote-tracking branch 'origin/xn-encdec-setup-messages' into integration_2026_w11 (!3923)

XNAP: Add encode/decode and unit tests for Xn Setup Request/Response/Failure

This MR adds complete support for the following in accordance with
3GPP TS 38.423 v16.2.0
- Add Xn Setup Request, Response, and Failure message type definitions
- Implement ASN.1 encode/decode for all Xn Setup messages
- Add equality checks and memory management helpers
- Create XNAP unit test infrastructure

Co-author: @venkatareddy

Acknowledgement
  This work was carried out as part of research and development at Indian
  Institute of Science (IISc), Bengaluru.

common/utils/LOG/log.h

@@ -162,6 +162,7 @@ static const char *const flag_name[] = {FOREACH_FLAG(FLAG_TEXT) ""};
   COMP_DEF(USIM, log)           \
   COMP_DEF(F1U, )               \
   COMP_DEF(X2AP, )              \
+  COMP_DEF(XNAP, )              \
   COMP_DEF(M2AP, )              \
   COMP_DEF(M3AP, )              \
   COMP_DEF(NGAP, )              \

common/utils/T/T_messages.txt

@@ -628,6 +628,27 @@ ID = LEGACY_X2AP_TRACE
     GROUP = ALL:LEGACY_X2AP:LEGACY_GROUP_TRACE:LEGACY
     FORMAT = string,log
 
+ID = LEGACY_XNAP_INFO
+    DESC = XNAP legacy logs - info level
+    GROUP = ALL:LEGACY_XNAP:LEGACY_GROUP_INFO:LEGACY
+    FORMAT = string,log
+ID = LEGACY_XNAP_ERROR
+    DESC = XNAP legacy logs - error level
+    GROUP = ALL:LEGACY_XNAP:LEGACY_GROUP_ERROR:LEGACY
+    FORMAT = string,log
+ID = LEGACY_XNAP_WARNING
+    DESC = XNAP legacy logs - warning level
+    GROUP = ALL:LEGACY_XNAP:LEGACY_GROUP_WARNING:LEGACY
+    FORMAT = string,log
+ID = LEGACY_XNAP_DEBUG
+    DESC = XNAP legacy logs - debug level
+    GROUP = ALL:LEGACY_XNAP:LEGACY_GROUP_DEBUG:LEGACY
+    FORMAT = string,log
+ID = LEGACY_XNAP_TRACE
+    DESC = XNAP legacy logs - trace level
+    GROUP = ALL:LEGACY_XNAP:LEGACY_GROUP_TRACE:LEGACY
+    FORMAT = string,log
+
 ID = LEGACY_M2AP_INFO
     DESC = M2AP legacy logs - info level
     GROUP = ALL:LEGACY_M2AP:LEGACY_GROUP_INFO:LEGACY