Core/SAI: implement SMART_ACTION_ATTACK_STOP

Unlike SMART_ACTION_AUTO_ATTACK, this action is actually stopping the entire attack procedure, rather than just hack-disabling auto-attacks. Keep in mind that this action requires a passive react state to prevent a immediate AttackStart ai reaction

(cherry picked from commit 152ea60116)

src/server/game/AI/SmartScripts/SmartScript.cpp

@@ -1209,6 +1209,13 @@ void SmartScript::ProcessAction(SmartScriptHolder& e, Unit* unit, uint32 var0, u
             }
             break;
         }
+        case SMART_ACTION_ATTACK_STOP:
+        {
+            for (WorldObject* target : targets)
+                if (Unit* unitTarget = target->ToUnit())
+                    unitTarget->AttackStop();
+            break;
+        }
         case SMART_ACTION_MOVE_OFFSET:
         {
             for (WorldObject* target : targets)

src/server/game/AI/SmartScripts/SmartScriptMgr.cpp

@@ -1778,6 +1778,7 @@ bool SmartAIMgr::IsEventValid(SmartScriptHolder& e)
         case SMART_ACTION_ALLOW_COMBAT_MOVEMENT:
         case SMART_ACTION_CALL_FOR_HELP:
         case SMART_ACTION_SET_DATA:
+        case SMART_ACTION_ATTACK_STOP:
         case SMART_ACTION_SET_VISIBILITY:
         case SMART_ACTION_WP_PAUSE:
         case SMART_ACTION_SET_DISABLE_GRAVITY:

src/server/game/AI/SmartScripts/SmartScriptMgr.h

@@ -512,6 +512,7 @@ enum SMART_ACTION
     SMART_ACTION_MOUNT_TO_ENTRY_OR_MODEL            = 43,     // Creature_template entry(param1) OR ModelId (param2) (or 0 for both to dismount)
     SMART_ACTION_SET_INGAME_PHASE_ID                = 44,     // PhaseId, apply
     SMART_ACTION_SET_DATA                           = 45,     // Field, Data (only creature @todo)
+    SMART_ACTION_ATTACK_STOP                        = 46,     //
     SMART_ACTION_SET_VISIBILITY                     = 47,     // on/off
     SMART_ACTION_SET_ACTIVE                         = 48,     // on/off
     SMART_ACTION_ATTACK_START                       = 49,     //