UI: Add the ability to change a DualSense/DualShock 4's LED color.

Not functional yet. This is the UI & persistence side of #572.

src/Ryujinx/UI/ViewModels/Input/ControllerInputViewModel.cs

@@ -37,7 +37,7 @@ namespace Ryujinx.Ava.UI.ViewModels.Input
 
         [ObservableProperty] private SvgImage _image;
 
-        public readonly InputViewModel ParentModel;
+        public InputViewModel ParentModel { get; }
 
         public ControllerInputViewModel(InputViewModel model, GamepadInputConfig config)
         {

src/Ryujinx/UI/ViewModels/Input/InputViewModel.cs

@@ -68,6 +68,8 @@ namespace Ryujinx.Ava.UI.ViewModels.Input
         public bool IsKeyboard => !IsController;
         public bool IsRight { get; set; }
         public bool IsLeft { get; set; }
+        
+        public bool HasLed => SelectedGamepad.Features.HasFlag(GamepadFeaturesFlag.Led);
 
         public bool IsModified { get; set; }
         public event Action NotifyChangesEvent;