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/Prepo/IPrepoService.cs

@@ -10,11 +10,11 @@ namespace Ryujinx.HLE.HOS.Services.Prepo
 
         [Command(10101)]
         // SaveReportWithUser(nn::account::Uid, u64, pid, buffer<u8, 9>, buffer<bytes, 5>)
-        public static long SaveReportWithUser(ServiceCtx context)
+        public static ResultCode SaveReportWithUser(ServiceCtx context)
         {
             Logger.PrintStub(LogClass.ServicePrepo);
 
-            return 0;
+            return ResultCode.Success;
         }
     }
 }