[ios] fix memory leak in RadioButton

Context: https://github.com/heyThorsten/GCTest
Fixes: #20023

In testing the above sample, a page with a `RadioButton` has a memory
leak due to the usage of `Border.StrokeShape`.

There was also a slight "rabbit" hole, where we thought there was also
an issue with `GestureRecognizers`. But this was not the case in a real
app (just unit tests):

* #21089

It turns out that when `GestureRecognizers` are used in `MemoryTests`,
they will leak if there is no `Window` involved.

Instead of using `MemoryTests` like I would traditionally, we should
instead use `NavigationPageTests.DoesNotLeak()`. I can reproduce the
problem with `RadioButton` *and* a `Window` exists in the test.

~~ Underlying issue ~~

It appears that `Border.StrokeShape` does not use the same pattern as
other properties like `Border.Stroke`:

* On set: `SetInheritedBindingContext(visualElement, BindingContext);`
* On unset: `SetInheritedBindingContext(visualElement, null);`

It instead used:

* On set: `AddLogicalChild(visualElement);`
* On unset: `RemoveLogicalChild(visualElement);`

6136a8a that introduced these does not mention why one was used over
another. I am unsure if this will cause a problem, but it fixes the leak.

src/Controls/src/Core/Border/Border.cs

@@ -64,7 +64,7 @@ void NotifyStrokeShapeChanges()
 
 			if (strokeShape is VisualElement visualElement)
 			{
-				AddLogicalChild(visualElement);
+				SetInheritedBindingContext(visualElement, BindingContext);
 				_strokeShapeChanged ??= (sender, e) => OnPropertyChanged(nameof(StrokeShape));
 				_strokeShapeProxy ??= new();
 				_strokeShapeProxy.Subscribe(visualElement, _strokeShapeChanged);
@@ -77,7 +77,7 @@ void StopNotifyingStrokeShapeChanges()
 
 			if (strokeShape is VisualElement visualElement)
 			{
-				RemoveLogicalChild(visualElement);
+				SetInheritedBindingContext(visualElement, null);
 				_strokeShapeProxy?.Unsubscribe();
 			}
 		}

src/Controls/tests/DeviceTests/Elements/NavigationPage/NavigationPageTests.cs

@@ -4,8 +4,10 @@
 using System.Text;
 using System.Threading.Tasks;
 using Microsoft.Maui.Controls;
+using Microsoft.Maui.Controls.Handlers;
 using Microsoft.Maui.Controls.Handlers.Compatibility;
 using Microsoft.Maui.Controls.Handlers.Items;
+using Microsoft.Maui.Controls.Shapes;
 using Microsoft.Maui.DeviceTests.Stubs;
 using Microsoft.Maui.Handlers;
 using Microsoft.Maui.Hosting;
@@ -33,15 +35,19 @@ void SetupBuilder()
 					handlers.AddHandler(typeof(TabbedPage), typeof(TabbedViewHandler));
 #endif
 					handlers.AddHandler(typeof(FlyoutPage), typeof(FlyoutViewHandler));
-					handlers.AddHandler<Page, PageHandler>();
-					handlers.AddHandler<Window, WindowHandlerStub>();
-					handlers.AddHandler<Frame, FrameRenderer>();
-					handlers.AddHandler<Label, LabelHandler>();
+					handlers.AddHandler(typeof(ScrollView), typeof(ScrollViewHandler));
+					handlers.AddHandler<Border, BorderHandler>();
 					handlers.AddHandler<Button, ButtonHandler>();
 					handlers.AddHandler<CarouselView, CarouselViewHandler>();
 					handlers.AddHandler<CollectionView, CollectionViewHandler>();
-					handlers.AddHandler(typeof(Controls.ContentView), typeof(ContentViewHandler));
-					handlers.AddHandler(typeof(ScrollView), typeof(ScrollViewHandler));
+					handlers.AddHandler<Frame, FrameRenderer>();
+					handlers.AddHandler<IContentView, ContentViewHandler>();
+					handlers.AddHandler<Label, LabelHandler>();
+					handlers.AddHandler<Layout, LayoutHandler>();
+					handlers.AddHandler<Page, PageHandler>();
+					handlers.AddHandler<RadioButton, RadioButtonHandler>();
+					handlers.AddHandler<Shape, ShapeViewHandler>();
+					handlers.AddHandler<Window, WindowHandlerStub>();
 				});
 			});
 		}
@@ -323,6 +329,7 @@ public async Task DoesNotLeak()
 						new ContentView(),
 						new Label(),
 						new ScrollView(),
+						new RadioButton(),
 					}
 				};
 				pageReference = new WeakReference(page);