Avalonia: Another Cleanup (#3494)

* Avalonia: Another Cleanup

This PR is a cleanup to the avalonia code recently added:

- Some XAML file are autoformatted like a previous PR.
- Dlc is renamed to DownloadableContent (Locale exclude).
- DownloadableContentManagerWindow is a bit improved (Fixes #3491).
- Some nits here and there.

* Fix GTK

* Remove AttachDebugDevTools

* Fix last warning

* Fix JSON fields

Ryujinx.Common/Configuration/DownloadableContentContainer.cs

@@ -0,0 +1,13 @@
+using System.Collections.Generic;
+using System.Text.Json.Serialization;
+
+namespace Ryujinx.Common.Configuration
+{
+    public struct DownloadableContentContainer
+    {
+        [JsonPropertyName("path")]
+        public string ContainerPath { get; set; }
+        [JsonPropertyName("dlc_nca_list")]
+        public List<DownloadableContentNca> DownloadableContentNcaList { get; set; }
+    }
+}