perf(do): Reduce CallbackManager allocations when no callbacks are re…

…gistered

src/Uno.UI/UI/Xaml/DependencyObjectStore.cs

@@ -779,13 +779,13 @@ internal IDisposable RegisterPropertyChangedCallback(DependencyProperty property
 
 			if (ReferenceEquals(callback.Target, ActualInstance))
 			{
-				return propertyDetails.CallbackManager.RegisterCallback(callback);
+				return propertyDetails.RegisterCallback(callback);
 			}
 			else
 			{
 				CreateWeakDelegate(callback, out var weakCallback, out var weakDelegateRelease);
 
-				var cookie = propertyDetails.CallbackManager.RegisterCallback(weakCallback);
+				var cookie = propertyDetails.RegisterCallback(weakCallback);
 
 				return new RegisterPropertyChangedCallbackForPropertyConditionalDisposable(
 					callback,
@@ -1905,7 +1905,7 @@ private void InvokeCallbacks(
 			}
 
 			// Raise the changes for the callbacks register through RegisterPropertyChangedCallback.
-			propertyDetails.CallbackManager.RaisePropertyChanged(actualInstanceAlias, eventArgs);
+			propertyDetails.RaisePropertyChanged(actualInstanceAlias, eventArgs);
 
 			// Raise the property change for generic handlers
 			for (var callbackIndex = 0; callbackIndex < _genericCallbacks.Data.Length; callbackIndex++)

src/Uno.UI/UI/Xaml/DependencyPropertyDetails.cs

@@ -52,8 +52,6 @@ public void Dispose()
 			}
 		}
 
-		public DependencyPropertyCallbackManager CallbackManager => _callbackManager ??= new DependencyPropertyCallbackManager();
-
 		public DependencyProperty Property { get; }
 
 		public PropertyMetadata Metadata => _metadata ??= Property.GetMetadata(_dependencyObjectType);
@@ -372,6 +370,12 @@ public override string ToString()
 			return $"DependencyPropertyDetails({Property.Name})";
 		}
 
+		internal IDisposable RegisterCallback(PropertyChangedCallback callback)
+			=> (_callbackManager ??= new DependencyPropertyCallbackManager()).RegisterCallback(callback);
+
+		internal void RaisePropertyChanged(DependencyObject actualInstanceAlias, DependencyPropertyChangedEventArgs eventArgs)
+			=> _callbackManager?.RaisePropertyChanged(actualInstanceAlias, eventArgs);
+
 		[Flags]
 		enum Flags
 		{