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/DownloadableContentNca.cs

@@ -0,0 +1,14 @@
+using System.Text.Json.Serialization;
+
+namespace Ryujinx.Common.Configuration
+{
+    public struct DownloadableContentNca
+    {
+        [JsonPropertyName("path")]
+        public string FullPath { get; set; }
+        [JsonPropertyName("title_id")]
+        public ulong  TitleId  { get; set; }
+        [JsonPropertyName("is_enabled")]
+        public bool   Enabled  { get; set; }
+    }
+}