Core/AI: Finally move the "is creature engaged" flag to be a property of the creature AI, where it honestly always belonged. Fixes #17981 and #23602 for real this time.

src/server/scripts/Commands/cs_debug.cpp

@@ -859,7 +859,7 @@ public:
         ThreatManager& mgr = target->GetThreatManager();
         if (!target->IsAlive())
         {
-            handler->PSendSysMessage("%s (GUID %u) is not alive.", target->GetName().c_str(), target->GetGUID().GetCounter());
+            handler->PSendSysMessage("%s (GUID %u) is not alive.%s", target->GetName().c_str(), target->GetGUID().GetCounter(), target->IsEngaged() ? " (It is, however, engaged. Huh?)" : "");
             return true;
         }