Define Value property of Setter as XAML content property (#745)

* Define Value property of Setter as XAML content property

* Fixed API compat build error

---------

Co-authored-by: Anjali Sheel <anjalisheel@microsoft.com>

Author: thomasclaudiushuber

src/Microsoft.DotNet.Wpf/ApiCompat/Baselines/PresentationFramework-ref.baseline.txt

@@ -40,6 +40,7 @@ CannotChangeAttribute : Attribute 'System.Windows.LocalizabilityAttribute' on 'S
 CannotChangeAttribute : Attribute 'System.Windows.LocalizabilityAttribute' on 'System.Windows.ResourceDictionary' changed from '[LocalizabilityAttribute(16)]' in the contract to '[LocalizabilityAttribute(LocalizationCategory.Ignore)]' in the implementation.
 CannotChangeAttribute : Attribute 'System.ComponentModel.DesignerSerializationVisibilityAttribute' on 'System.Windows.ResourceDictionary.DeferrableContent' changed from '[DesignerSerializationVisibilityAttribute(0)]' in the contract to '[DesignerSerializationVisibilityAttribute(DesignerSerializationVisibility.Hidden)]' in the implementation.
 CannotChangeAttribute : Attribute 'System.ComponentModel.DesignerSerializationVisibilityAttribute' on 'System.Windows.ResourceDictionary.Source' changed from '[DesignerSerializationVisibilityAttribute(0)]' in the contract to '[DesignerSerializationVisibilityAttribute(DesignerSerializationVisibility.Hidden)]' in the implementation.
+CannotRemoveAttribute : Attribute 'System.Windows.Markup.ContentPropertyAttribute' exists on 'System.Windows.Setter' in the contract but not the implementation.
 CannotChangeAttribute : Attribute 'System.Windows.LocalizabilityAttribute' on 'System.Windows.Setter.Property' changed from '[LocalizabilityAttribute(0, Modifiability=0, Readability=0)]' in the contract to '[LocalizabilityAttribute(LocalizationCategory.None, Modifiability=Modifiability.Unmodifiable, Readability=Readability.Unreadable)]' in the implementation.
 CannotChangeAttribute : Attribute 'System.Windows.LocalizabilityAttribute' on 'System.Windows.Setter.Value' changed from '[LocalizabilityAttribute(0, Readability=0)]' in the contract to '[LocalizabilityAttribute(LocalizationCategory.None, Readability=Readability.Unreadable)]' in the implementation.
 CannotChangeAttribute : Attribute 'System.Windows.LocalizabilityAttribute' on 'System.Windows.SetterBase' changed from '[LocalizabilityAttribute(16)]' in the contract to '[LocalizabilityAttribute(LocalizationCategory.Ignore)]' in the implementation.
@@ -261,4 +262,4 @@ CannotChangeAttribute : Attribute 'System.ComponentModel.DesignerSerializationVi
 CannotChangeAttribute : Attribute 'System.Windows.Markup.DesignerSerializationOptionsAttribute' on 'System.Windows.Markup.XmlAttributeProperties.GetXmlSpace(System.Windows.DependencyObject)' changed from '[DesignerSerializationOptionsAttribute(1)]' in the contract to '[DesignerSerializationOptionsAttribute(DesignerSerializationOptions.SerializeAsAttribute)]' in the implementation.
 CannotChangeAttribute : Attribute 'System.ComponentModel.DesignerSerializationVisibilityAttribute' on 'System.Windows.Media.Animation.Storyboard.GetTarget(System.Windows.DependencyObject)' changed from '[DesignerSerializationVisibilityAttribute(0)]' in the contract to '[DesignerSerializationVisibilityAttribute(DesignerSerializationVisibility.Hidden)]' in the implementation.
 CannotChangeAttribute : Attribute 'System.Windows.LocalizabilityAttribute' on 'System.Windows.Shapes.Shape' changed from '[LocalizabilityAttribute(0, Readability=0)]' in the contract to '[LocalizabilityAttribute(LocalizationCategory.None, Readability=Readability.Unreadable)]' in the implementation.
-Total Issues: 262
+Total Issues: 263

src/Microsoft.DotNet.Wpf/ApiCompat/Baselines/System.Windows.Controls.Ribbon-ref-Net48.baseline.txt

@@ -1,2 +1 @@
-Compat issues with assembly System.Windows.Controls.Ribbon:
 Total Issues: 0

src/Microsoft.DotNet.Wpf/ApiCompat/Baselines/UIAutomationProvider-ref.baseline.txt

@@ -11,7 +11,6 @@ CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeA
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.IRawElementProviderFragment' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.IRawElementProviderFragmentRoot' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.IRawElementProviderHwndOverride' in the contract but not the implementation.
-CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.IRawElementProviderSimple' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.IScrollItemProvider' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.IScrollProvider' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.ISelectionItemProvider' in the contract but not the implementation.
@@ -20,10 +19,9 @@ CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeA
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.ITableItemProvider' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.ITableProvider' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.ITextProvider' in the contract but not the implementation.
-CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.ITextRangeProvider' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.IToggleProvider' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.ITransformProvider' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.IValueProvider' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.IVirtualizedItemProvider' in the contract but not the implementation.
 CannotRemoveAttribute : Attribute 'System.Runtime.InteropServices.InterfaceTypeAttribute' exists on 'System.Windows.Automation.Provider.IWindowProvider' in the contract but not the implementation.
-Total Issues: 27
+Total Issues: 25

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Setter.cs

@@ -24,6 +24,7 @@ namespace System.Windows
     /// </summary>
     [XamlSetMarkupExtensionAttribute("ReceiveMarkupExtension")]
     [XamlSetTypeConverterAttribute("ReceiveTypeConverter")] 
+    [ContentProperty("Value")]
     public class Setter : SetterBase, ISupportInitialize
     {
         /// <summary>