add Presented event

From DeviceTests, there's a case where the DialogFragment is shown, but the animation event isn't fired, maybe it's dismissed before the animation completes. So adding a handler that will inform that Dialog is shown after 500ms, avoid a dead-lock

src/Controls/src/Core/Platform/ModalNavigationManager/ModalNavigationManager.Android.cs

@@ -8,6 +8,7 @@
 using Android.Runtime;
 using Android.Views;
 using System.Runtime.CompilerServices;
+using System.Threading;
 using Android.Views.Animations;
 using AndroidX.Fragment.App;
 using AAnimation = Android.Views.Animations.Animation;
@@ -201,37 +202,49 @@ async Task PresentModal(Page modal, bool animated)
 			var fragmentManager = WindowMauiContext.GetFragmentManager();
 			var dialogFragmentId = AView.GenerateViewId().ToString();
 			_modals.Push(dialogFragmentId);
-			dialogFragment.Show(fragmentManager, dialogFragmentId);
-
+
 			if (animated)
 			{
 				NavAnimationInProgress = true;
-				dialogFragment!.AnimationEnded += OnAnimationEnded;
+				dialogFragment.AnimationEnded += OnAnimationEnded;
+				dialogFragment.Presented += OnPresented;
+
+				dialogFragment.Show(fragmentManager, dialogFragmentId);
+
+				void OnPresented(object? sender, EventArgs e)
+				{
+					dialogFragment.AnimationEnded -= OnAnimationEnded;
+					NavAnimationInProgress = false;
+					animationCompletionSource.SetResult(true);
+				}
 
 				await animationCompletionSource.Task;
 			}
 			else
 			{
+
+				dialogFragment.Show(fragmentManager, dialogFragmentId);
 				NavAnimationInProgress = false;
 				animationCompletionSource.TrySetResult(true);
 			}
 
 			void OnAnimationEnded(object? sender, EventArgs e)
 			{
-				dialogFragment!.AnimationEnded -= OnAnimationEnded;
+				dialogFragment.AnimationEnded -= OnAnimationEnded;
 				NavAnimationInProgress = false;
 				animationCompletionSource.SetResult(true);
 			}
 		}
 
-		internal class ModalFragment : DialogFragment
+		internal sealed class ModalFragment : DialogFragment
 		{
 			Page _modal;
 			IMauiContext _mauiWindowContext;
 			NavigationRootManager? _navigationRootManager;
 			static readonly ColorDrawable TransparentColorDrawable = new(AColor.Transparent);
 
 			public event EventHandler? AnimationEnded;
+			public event EventHandler? Presented;
 
 
 			public bool IsAnimated { get; internal set; }
@@ -285,6 +298,9 @@ public override void OnStart()
 				int height = ViewGroup.LayoutParams.MatchParent;
 				dialog.Window.SetLayout(width, height);
 
+
+				var cts = new CancellationTokenSource(TimeSpan.FromMilliseconds(700));
+				var tcs = new TaskCompletionSource();
 				if (IsAnimated)
 				{
 					var animation = AnimationUtils.LoadAnimation(_mauiWindowContext.Context, Resource.Animation.nav_modal_default_enter_anim)!;
@@ -293,14 +309,24 @@ public override void OnStart()
 					animation.AnimationEnd += OnAnimationEnded;
 				}
 
+				tcs.Task.WaitAsync(cts.Token).ContinueWith(t =>
+				{
+					cts.Dispose();
+					Presented?.Invoke(this, EventArgs.Empty);
+
+				}, CancellationToken.None, TaskContinuationOptions.OnlyOnCanceled, TaskScheduler.FromCurrentSynchronizationContext());
+
 				void OnAnimationEnded(object? sender, AAnimation.AnimationEndEventArgs e)
 				{
 					if (sender is not AAnimation animation)
 					{
 						return;
 					}
 
+					tcs.TrySetResult();
+
 					animation.AnimationEnd -= OnAnimationEnded;
+					cts.Dispose();
 					AnimationEnded?.Invoke(this, EventArgs.Empty);
 				}
 			}