Refactoring result codes (#731)

* refactoring result codes

- Add a main enum who can handle some orphalin result codes and the default `ResultCode.Success` one.
- Add sub-enum by services when it's needed.
- Remove some empty line.
- Recast all service calls to ResultCode.
- Remove some unneeded static declaration.
- Delete unused `NvHelper` class.

* NvResult is back

* Fix

Ryujinx.HLE/HOS/Services/Vi/IManagerRootService.cs

@@ -7,13 +7,13 @@ namespace Ryujinx.HLE.HOS.Services.Vi
 
         [Command(2)]
         // GetDisplayService(u32) -> object<nn::visrv::sf::IApplicationDisplayService>
-        public long GetDisplayService(ServiceCtx context)
+        public ResultCode GetDisplayService(ServiceCtx context)
         {
             int serviceType = context.RequestData.ReadInt32();
 
             MakeObject(context, new IApplicationDisplayService());
 
-            return 0;
+            return ResultCode.Success;
         }
     }
 }