[Windows] Fixed Margin doesn't work inside CollectionView EmptyView (#29897)

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### Issue Detail
The Margin property is not applied as expected when used within the
EmptyView of a CollectionView.
 
Note: Issue not replicated in Android, iOS and Mac platforms in latest.
 
### Root Cause
The Margin set on the EmptyView is not automatically applied to the
native container (ContentControl) on the Windows platform, resulting in
incorrect layout spacing.
 
### Description of Change
Applied the EmptyView’s Margin explicitly to the _emptyView.Marging to
ensure consistent layout rendering on Windows.
 
### Validated the behaviour in the following platforms
 
- [x] Android
- [x] Windows
- [x] iOS
- [x] Mac
 
### Issues Fixed:
Fixes #8494 
 
### Screenshots
| Before  | After |
|---------|--------|
| <img
src="https://github.com/user-attachments/assets/23f75266-60ec-4888-a177-bc484178c000">
| <img
src="https://github.com/user-attachments/assets/6e9593df-f7fb-433c-994d-8462d6c528ac">
|

Author: Dhivya-SF4094

src/Controls/src/Core/Handlers/Items/ItemsViewHandler.Windows.cs

@@ -350,6 +350,12 @@ protected virtual void UpdateEmptyView()
 					break;
 			}
 
+			if (_formsEmptyView is not null && _emptyView is not null)
+			{
+				var margin = _formsEmptyView.Margin;
+				_emptyView.Margin = WinUIHelpers.CreateThickness(margin.Left, margin.Top, margin.Right, margin.Bottom);
+			}
+
 			(ListViewBase as IEmptyView)?.SetEmptyView(_emptyView, _formsEmptyView);
 
 			UpdateEmptyViewVisibility();

src/Controls/tests/TestCases.Android.Tests/snapshots/android/CheckEmptyViewMargin.png

@@ -0,0 +1,66 @@
+using System.Collections.ObjectModel;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 8494, "Margin doesn't work inside CollectionView EmptyView", PlatformAffected.UWP)]
+
+public class Issue8494 : ContentPage
+{
+	Issue8494EmptyViewModel ViewModel;
+
+	public Issue8494()
+	{
+		ViewModel = new Issue8494EmptyViewModel();
+		BindingContext = ViewModel;
+		var label = new Label
+		{
+			Text = "EmptyView should be laid out with respect to the Specified margin",
+			AutomationId = "EmptyViewDescriptionLabel",
+		};
+
+		var emptyViewLayout = new StackLayout
+		{
+			Margin = new Thickness(40),
+			Background = Colors.Yellow,
+			Children =
+				{
+					new Label
+					{
+						Text = "EmptyView with Margin.",
+						BackgroundColor = Colors.Blue,
+						HorizontalTextAlignment = TextAlignment.Center,
+					},
+				}
+		};
+
+		var collectionView = new CollectionView
+		{
+			ItemsSource = ViewModel.ItemList,
+			BackgroundColor = Colors.Green,
+			EmptyView = emptyViewLayout,
+		};
+
+		var grid = new Grid
+		{
+			RowDefinitions =
+			{
+				new RowDefinition { Height = GridLength.Auto },
+				new RowDefinition { Height = GridLength.Star },
+			}
+		};
+
+		grid.Add(label, 0, 0);
+		grid.Add(collectionView, 0, 1);
+		Content = grid;
+	}
+}
+
+public class Issue8494EmptyViewModel
+{
+	public ObservableCollection<string> ItemList { get; set; }
+
+	public Issue8494EmptyViewModel()
+	{
+		ItemList = new ObservableCollection<string>();
+	}
+}

src/Controls/tests/TestCases.HostApp/Issues/Issue8494.cs

@@ -0,0 +1,21 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue8494 : _IssuesUITest
+{
+	public Issue8494(TestDevice testDevice) : base(testDevice)
+	{
+	}
+	public override string Issue => "Margin doesn't work inside CollectionView EmptyView";
+
+	[Test]
+	[Category(UITestCategories.CollectionView)]
+	public void CheckEmptyViewMargin()
+	{
+		App.WaitForElement("EmptyViewDescriptionLabel");
+		VerifyScreenshot();
+	}
+}