misc: move Models & Helpers into Common & Avalonia projects

src/Ryujinx/Utilities/AppLibrary/LdnGameDataSerializerContext.cs

@@ -0,0 +1,8 @@
+using System.Collections.Generic;
+using System.Text.Json.Serialization;
+
+namespace Ryujinx.Ava.Utilities.AppLibrary
+{
+    [JsonSerializable(typeof(IEnumerable<LdnGameData>))]
+    internal partial class LdnGameDataSerializerContext : JsonSerializerContext;
+}