Core/Spells: SpellAttr8 fixups - use creator instead of owner for SPELL_ATTR8_ONLY_TARGET_IF_SAME_CREATOR and removed cast time requirement for channelled spell predicted healing

Port From (https://github.com/TrinityCore/TrinityCore/commit/930a08fe03a033a6bb30fb8c94a8490c4b77fe91)

Source/Game/Entities/Object/WorldObject.cs

@@ -3121,6 +3121,7 @@ namespace Game.Entities
 
         public virtual bool LoadFromDB(ulong spawnId, Map map, bool addToMap, bool allowDuplicate) { return true; }
 
+        public virtual ObjectGuid GetCreatorGUID() { return default; }
         public virtual ObjectGuid GetOwnerGUID() { return default; }
         public virtual ObjectGuid GetCharmerOrOwnerGUID() { return GetOwnerGUID(); }