Remove DLW's special lifetime handling

osu.Framework.Tests/Visual/Drawables/TestSceneDelayedLoadWrapper.cs

···
             AddUntilStep("repeating schedulers removed", () => !scroll.Scheduler.HasPendingTasks);
         }
 
-        [Test]
-        public void TestLifetimeOutwardsPropagation()
-        {
-            Container wrapped = null;
-            DelayedLoadWrapper wrapper = null;
-
-            AddStep("create child", () =>
-            {
-                flow.Add(new Container
-                {
-                    Size = new Vector2(128),
-                    Children = new Drawable[]
-                    {
-                        wrapper = new DelayedLoadWrapper(wrapped = new Container
-                        {
-                            RelativeSizeAxes = Axes.Both,
-                            Children = new Drawable[]
-                            {
-                                new TestBox(() => loaded++) { RelativeSizeAxes = Axes.Both }
-                            }
-                        }),
-                    }
-                });
-
-                wrapper.DelayedLoadComplete += content => content.FadeOut(500).Expire();
-            });
-
-            AddAssert("wrapper lifetime equals content lifetime", () => wrapper.LifetimeEnd == wrapped.LifetimeEnd);
-
-            AddUntilStep("wrapper expired", () => !wrapper.IsAlive);
-        }
-
-        [Test]
-        public void TestLifetimeInwardsPropagation()
-        {
-            Container wrapped = null;
-            DelayedLoadWrapper wrapper = null;
-            double lifetimeEnd = 0;
-
-            AddStep("create child", () =>
-            {
-                flow.Add(new Container
-                {
-                    Size = new Vector2(128),
-                    Children = new Drawable[]
-                    {
-                        wrapper = new DelayedLoadWrapper(wrapped = new Container
-                        {
-                            // this lifetime will be overwritten by the one on the wrapper.
-                            LifetimeEnd = Time.Current + 4000,
-                            RelativeSizeAxes = Axes.Both,
-                            Children = new Drawable[]
-                            {
-                                new TestBox(() => loaded++) { RelativeSizeAxes = Axes.Both }
-                            }
-                        })
-                        {
-                            LifetimeEnd = lifetimeEnd = Time.Current + 2000,
-                        }
-                    }
-                });
-            });
-
-            AddUntilStep("wait for load", () => wrapper.DelayedLoadCompleted);
-
-            AddAssert("wrapper lifetime is correct", () => wrapper.LifetimeEnd == lifetimeEnd);
-            AddAssert("content lifetime is correct", () => wrapped.LifetimeEnd == lifetimeEnd);
-
-            AddUntilStep("wrapper expired", () => !wrapper.IsAlive);
-        }
-
         [TestCase(false)]
         [TestCase(true)]
         public void TestManyChildrenFunction(bool instant)

osu.Framework/Graphics/Containers/DelayedLoadWrapper.cs

···
     /// Has the ability to delay the loading until it has been visible on-screen for a specified duration.
     /// In order to benefit from delayed load, we must be inside a <see cref="ScrollContainer{T}"/>.
     /// </summary>
-    /// <remarks>
-    /// <see cref="LifetimeStart"/> and <see cref="LifetimeEnd"/> are propagated from the wrapper to the content on content load.
-    /// After load, the content's lifetime is preferred, meaning any changes to content's lifetime post-load will be respected.
-    /// </remarks>
     public class DelayedLoadWrapper : CompositeDrawable
     {
         [Resolved]
···
 
             AddLayout(optimisingContainerCache);
             AddLayout(isIntersectingCache);
-        }
-
-        private double lifetimeStart = double.MinValue;
-
-        public override double LifetimeStart
-        {
-            get => Content?.LifetimeStart ?? lifetimeStart;
-            set
-            {
-                if (Content != null)
-                    Content.LifetimeStart = value;
-                lifetimeStart = value;
-            }
-        }
-
-        private double lifetimeEnd = double.MaxValue;
-
-        public override double LifetimeEnd
-        {
-            get => Content?.LifetimeEnd ?? lifetimeEnd;
-            set
-            {
-                if (Content != null)
-                    Content.LifetimeEnd = value;
-                lifetimeEnd = value;
-            }
         }
 
         private Drawable content;
···
             // This code is running on the game's scheduler, while this DLW may have been async disposed, so the addition is scheduled locally to prevent adding to disposed DLWs.
             scheduledAddition = Schedule(() =>
             {
-                content.LifetimeStart = lifetimeStart;
-                content.LifetimeEnd = lifetimeEnd;
-
                 AddInternal(content);
 
                 DelayedLoadCompleted = true;