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/Pm/IShellInterface.cs

@@ -7,7 +7,7 @@
 
         [Command(6)]
         // GetApplicationPid() -> u64
-        public long GetApplicationPid(ServiceCtx context)
+        public ResultCode GetApplicationPid(ServiceCtx context)
         {
             // FIXME: This is wrong but needed to make hb loader works
             // TODO: Change this when we will have a way to process via a PM like interface.
@@ -15,7 +15,7 @@
 
             context.ResponseData.Write(pid);
 
-            return 0;
+            return ResultCode.Success;
         }
     }
 }