[Testing] Navigate directly to control tests (#25242)

* Like with issues, set gallery items as mainpage directly

* More changes

src/Controls/tests/TestCases.HostApp/CoreViews/CoreGalleryBasePage.cs

@@ -48,10 +48,10 @@ namespace Maui.Controls.Sample
 					new Button()
 					{
 						Text = "Dismiss Page",
-						Command = new Command(async () =>
+						Command = new Command(() =>
 						{
 							if (_picker.SelectedIndex == 0)
-								await Navigation.PopAsync();
+								Application.Current.Quit();
 							else
 								_picker.SelectedIndex--;
 						})

src/Controls/tests/TestCases.HostApp/CoreViews/CorePageView.cs

@@ -123,7 +123,7 @@ namespace Maui.Controls.Sample
 			ItemTemplate = template;
 			ItemsSource = _pages;
 
-			ItemSelected += async (sender, args) =>
+			ItemSelected += (sender, args) =>
 			{
 				if (SelectedItem == null)
 				{
@@ -134,14 +134,8 @@ namespace Maui.Controls.Sample
 				if (item is GalleryPageFactory page)
 				{
 					var realize = page.Realize();
-					if (realize is Shell)
-					{
-						Application.Current.MainPage = realize;
-					}
-					else
-					{
-						await PushPage(realize);
-					}
+
+					Application.Current.MainPage = realize;
 				}
 
 				SelectedItem = null;