Code formatting updates (#4502)

* Editorconfig: Add space_before_self_closing setting

This was a difference between the way dotnet-format and Rider format code. See https://www.jetbrains.com/help/rider/EditorConfig_Index.html

* Editorconfig: Keep 4 spaces indentation for Swagger JSON files

They are all formatted that way, let's keep it like that.

* Apply dotnet-format, mostly white-space related changes

BTCPayServer.Client/Models/RateSource.cs

@@ -1,7 +1,7 @@
-namespace BTCPayServer.Client.Models;
+namespace BTCPayServer.Client.Models;
 
 public class RateSource
 {
     public string Id { get; set; }
     public string Name { get; set; }
-}
+}