Core/Creature: rename CREATURE_FLAG_EXTRA_IGNORE_COMBAT into CREATURE_FLAG_EXTRA_CANNOT_ENTER_COMBAT

Port From (https://github.com/TrinityCore/TrinityCore/commit/53d19b09f4de7c092747663ae7e1a01c0df553bf)

Source/Game/Entities/Unit/Unit.Fields.cs

@@ -55,7 +55,7 @@ namespace Game.Entities
         uint[] m_baseAttackSpeed = new uint[(int)WeaponAttackType.Max];
         internal float[] m_modAttackSpeedPct = new float[(int)WeaponAttackType.Max];
         protected uint[] m_attackTimer = new uint[(int)WeaponAttackType.Max];
-        bool _isIgnoringCombat;
+        bool _isCombatDisallowed;
 
         // Threat+combat management
         CombatManager m_combatManager;