Refactoring HOS folder structure (#771)

* Refactoring HOS folder structure

Refactoring HOS folder structure:

- Added some subfolders when needed (Following structure decided in private).
- Added some `Types` folders when needed.
- Little cleanup here and there.
- Add services placeholders for every HOS services (close #766 and #753).

* Remove Types namespaces

Ryujinx.HLE/HOS/Services/Prepo/IPrepoService.cs

@@ -3,6 +3,7 @@ using Ryujinx.Common.Logging;
 namespace Ryujinx.HLE.HOS.Services.Prepo
 {
     [Service("prepo:a")]
+    [Service("prepo:a2")]
     [Service("prepo:u")]
     class IPrepoService : IpcService
     {