refactor(Core/ObjectMgr): Load Creatures.CustomIDs into stores (#14835)

src/server/game/Globals/ObjectMgr.h

@@ -672,6 +672,8 @@ typedef std::unordered_map<uint32, VendorItemData> CacheVendorItemContainer;
 typedef std::unordered_map<uint32, TrainerSpellData> CacheTrainerSpellContainer;
 typedef std::unordered_map<uint32, ServerMail> ServerMailContainer;
 
+typedef std::vector<uint32> CreatureCustomIDsContainer;
+
 enum SkillRangeType
 {
     SKILL_RANGE_LANGUAGE,                                   // 300..300
@@ -1020,6 +1022,7 @@ public:
     void LoadCreatureTemplateAddons();
     void LoadCreatureTemplateResistances();
     void LoadCreatureTemplateSpells();
+    void LoadCreatureCustomIDs();
     void CheckCreatureTemplate(CreatureTemplate const* cInfo);
     void CheckCreatureMovement(char const* table, uint64 id, CreatureMovementData& creatureMovement);
     void LoadGameObjectQuestItems();
@@ -1555,6 +1558,7 @@ private:
     CellObjectGuids _emptyCellObjectGuids;
     CreatureDataContainer _creatureDataStore;
     CreatureTemplateContainer _creatureTemplateStore;
+    CreatureCustomIDsContainer _creatureCustomIDsStore;
     std::vector<CreatureTemplate*> _creatureTemplateStoreFast; // pussywizard
     CreatureModelContainer _creatureModelStore;
     CreatureAddonContainer _creatureAddonStore;