fix(Core/Creatures): Implemented `SUMMON_PROP_FLAG_ONLY_VISIBLE_TO_SU… (#14054)

* fix(Core/Creatures): Implemented `SUMMON_PROP_FLAG_ONLY_VISIBLE_TO_SUMMONER` summon flag.

Fixes #6674

* Update.

src/server/game/Entities/Creature/TemporarySummon.cpp

@@ -25,7 +25,7 @@
 
 TempSummon::TempSummon(SummonPropertiesEntry const* properties, ObjectGuid owner, bool isWorldObject) :
     Creature(isWorldObject), m_Properties(properties), m_type(TEMPSUMMON_MANUAL_DESPAWN),
-    m_timer(0), m_lifetime(0)
+    m_timer(0), m_lifetime(0), _visibleBySummonerOnly(false)
 {
     if (owner)
     {

src/server/game/Entities/Creature/TemporarySummon.h

@@ -57,14 +57,19 @@ public:
     uint32 GetTimer() { return m_timer; }
     void SetTimer(uint32 t) { m_timer = t; }
 
+    void SetVisibleBySummonerOnly(bool visibleBySummonerOnly) { _visibleBySummonerOnly = visibleBySummonerOnly; }
+    [[nodiscard]] bool IsVisibleBySummonerOnly() const { return _visibleBySummonerOnly; }
+
     const SummonPropertiesEntry* const m_Properties;
 
     std::string GetDebugInfo() const override;
+
 private:
     TempSummonType m_type;
     uint32 m_timer;
     uint32 m_lifetime;
     ObjectGuid m_summonerGUID;
+    bool _visibleBySummonerOnly;
 };
 
 class Minion : public TempSummon