Core/Movement: Ensure land and takeoff animations even if gravity enabled/disabled state is not what spline generator expects

Port From (https://github.com/TrinityCore/TrinityCore/commit/be3ae90dc488894afea8e4cca74d9105558fff53)

Source/Game/Movement/Generators/MovementGenerators.cs

@@ -17,6 +17,12 @@ namespace Game.Movement
         public UnitState BaseUnitState;
         public TaskCompletionSource<MovementStopReason> ScriptResult;
 
+        ~MovementGenerator()
+        {
+            // Ensure script doesn't get stuck waiting for this movement
+            SetScriptResult(MovementStopReason.Interrupted);
+        }
+
         // on top first update
         public virtual void Initialize(Unit owner) { }