[ImageResizer] Fix issues with blank Width and Height controls (#37373)

* Allow custom preset's dimensions to be blank in the UI while still persisted as 0.

* XAML formatting - reorder namespaces.

* Add "(auto)" text to zero-value Width/Height in Settings. Ensure Width and Height fields in flyout are formatted to empty when their value is 0.

src/modules/imageresizer/ui/App.xaml

@@ -21,6 +21,8 @@
             <v:VisibilityBoolConverter x:Key="VisibilityBoolConverter" />
             <v:EnumToIntConverter x:Key="EnumToIntConverter" />
             <v:AccessTextToTextConverter x:Key="AccessTextToTextConverter" />
+            <v:NumberBoxValueConverter x:Key="NumberBoxValueConverter" />
+            <v:ZeroToEmptyStringNumberFormatter x:Key="ZeroToEmptyStringNumberFormatter" />
         </ResourceDictionary>
     </Application.Resources>
 </Application>