Core/Movement: Add new flag MOVEMENTGENERATOR_FLAG_PERSIST_ON_DEATH

Port From (https://github.com/TrinityCore/TrinityCore/commit/8111f50d035c1915165cb8ecd4938ba97820ed10)

Source/Framework/Constants/Movement/MovementConst.cs

@@ -97,6 +97,7 @@ namespace Framework.Constants
         Deactivated = 0x040,
         InformEnabled = 0x080,
         Finalized = 0x100,
+        PersistOnDeath = 0x200,
 
         Transitory = SpeedUpdatePending | Interrupted
     }

Source/Game/Entities/Unit/Unit.cs

@@ -1397,18 +1397,8 @@ namespace Game.Entities
                 // Don't clear the movement if the Unit was on a vehicle as we are exiting now
                 if (!isOnVehicle)
                 {
-                    if (IsInWorld)
-                    {
-                        // Only clear MotionMaster for entities that exists in world
-                        // Avoids crashes in the following conditions :
-                        //  * Using 'call pet' on dead pets
-                        //  * Using 'call stabled pet'
-                        //  * Logging in with dead pets
-                        GetMotionMaster().Clear();
-                        GetMotionMaster().MoveIdle();
-                    }
-                    StopMoving();
-                    DisableSpline();
+                    if (GetMotionMaster().StopOnDeath())
+                        DisableSpline();
                 }
 
                 // without this when removing IncreaseMaxHealth aura player may stuck with 1 hp

Source/Game/Movement/MotionMaster.cs

@@ -513,6 +513,29 @@ namespace Game.Movement
             return true;
         }
 
+        public bool StopOnDeath()
+        {
+            MovementGenerator movementGenerator = GetCurrentMovementGenerator();
+            if (movementGenerator != null)
+                if (movementGenerator.HasFlag(MovementGeneratorFlags.PersistOnDeath))
+                    return false;
+
+            if (_owner.IsInWorld)
+            {
+                // Only clear MotionMaster for entities that exists in world
+                // Avoids crashes in the following conditions :
+                //  * Using 'call pet' on dead pets
+                //  * Using 'call stabled pet'
+                //  * Logging in with dead pets
+                Clear();
+                MoveIdle();
+            }
+
+            _owner.StopMoving();
+
+            return true;
+        }
+
         public void MoveIdle()
         {
             Add(GetIdleMovementGenerator(), MovementSlot.Default);
@@ -710,6 +733,7 @@ namespace Game.Movement
 
             GenericMovementGenerator movement = new(init, MovementGeneratorType.Effect, 0);
             movement.Priority = MovementGeneratorPriority.Highest;
+            movement.AddFlag(MovementGeneratorFlags.PersistOnDeath);
             Add(movement);
         }
 
@@ -793,6 +817,7 @@ namespace Game.Movement
             GenericMovementGenerator movement = new GenericMovementGenerator(init, MovementGeneratorType.Effect, id, arrivalSpellId, arrivalSpellTargetGuid);
             movement.Priority = MovementGeneratorPriority.Highest;
             movement.BaseUnitState = UnitState.Jumping;
+            movement.AddFlag(MovementGeneratorFlags.PersistOnDeath);
             Add(movement);
         }