Fix missing string enum converters for the config (#4634)

* Fix missing string enum converters for the config

* Revert changing KeyboardHotkeys to struct

This needs to be done because
Avalonia's TwoWay Binding breaks otherwise.

Ryujinx.Common/Configuration/Hid/Controller/GamepadInputId.cs

@@ -1,5 +1,9 @@
-namespace Ryujinx.Common.Configuration.Hid.Controller
+using Ryujinx.Common.Utilities;
+using System.Text.Json.Serialization;
+
+namespace Ryujinx.Common.Configuration.Hid.Controller
 {
+    [JsonConverter(typeof(TypedStringEnumConverter<GamepadInputId>))]
     public enum GamepadInputId : byte
     {
         Unbound,
@@ -51,4 +55,4 @@
 
         Count
     }
-}
+}