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/Vi/IApplicationRootService.cs

@@ -1,3 +1,5 @@
+using Ryujinx.HLE.HOS.Services.Vi.RootService;
+
 namespace Ryujinx.HLE.HOS.Services.Vi
 {
     [Service("vi:u")]