Core/Movement: Store adv flying speeds instead of hardcoding them in SMSG_UPDATE_OBJECT and enable packets modifying them

Port From (https://github.com/TrinityCore/TrinityCore/commit/43c7965d6b97a919ddd7e97a1f6e3f5750553f09)

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

@@ -23,6 +23,7 @@ namespace Game.Entities
 
         //Movement
         protected float[] m_speed_rate = new float[(int)UnitMoveType.Max];
+        float[] m_advFlyingSpeed = new float[(int)AdvFlyingRateTypeSingle.Max];
         List<AbstractFollower> m_followingMe = new();
         public MoveSpline MoveSpline { get; set; }
         MotionMaster i_motionMaster;