[Shell] Changed TitleProperty From TwoWay to OneWay (#29280)

* Make TitleProperty OneWay

* Added a unit test

Author: kubaflo

src/Controls/src/Core/Shell/BaseShellItem.cs

@@ -51,7 +51,7 @@ public class BaseShellItem : NavigableElement, IPropertyPropagationController, I
 
 		/// <summary>Bindable property for <see cref="Title"/>.</summary>
 		public static readonly BindableProperty TitleProperty =
-			BindableProperty.Create(nameof(Title), typeof(string), typeof(BaseShellItem), null, BindingMode.TwoWay, propertyChanged: OnTitlePropertyChanged);
+			BindableProperty.Create(nameof(Title), typeof(string), typeof(BaseShellItem), null, BindingMode.OneWay, propertyChanged: OnTitlePropertyChanged);
 
 		/// <summary>Bindable property for <see cref="IsVisible"/>.</summary>
 		public static readonly BindableProperty IsVisibleProperty =

src/Controls/tests/Core.UnitTests/ShellTests.cs

@@ -1645,5 +1645,34 @@ public async Task ShellSectionChangedFires()
 			Assert.Equal(shell.CurrentPage, page2);
 			Assert.True(fired);
 		}
+
+		[Fact]
+		public void ShellContentTitleShouldNotBeAppliedMultipleTimesWithStringFormat()
+		{
+			var theLabel = new Label
+			{
+				Text = "Hello, World!",
+				AutomationId = "theLabel"
+			};
+
+			var contentPage = new ContentPage
+			{
+				Content = theLabel
+			};
+
+			ShellContent shellContent = new ShellContent
+			{
+				Content = contentPage,
+			};
+
+			shellContent.SetBinding(ShellContent.TitleProperty, new Binding
+			{
+				Source = theLabel,
+				Path = "Text",
+				StringFormat = "Title: {0}"
+			});
+
+			Assert.Equal("Title: Hello, World!", shellContent.Title);
+		}
 	}
 }