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/Friend/FriendServicePermissionLevel.cs

@@ -16,4 +16,4 @@ namespace Ryujinx.HLE.HOS.Services.Friend
         Manager = UserMask | OverlayMask | ManagerMask,
         System  = UserMask | SystemMask
     }
-}
+}