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/Spl/IRandomInterface.cs

@@ -15,7 +15,7 @@ namespace Ryujinx.HLE.HOS.Services.Spl
 
         [Command(0)]
         // GetRandomBytes() -> buffer<unknown, 6>
-        public long GetRandomBytes(ServiceCtx context)
+        public ResultCode GetRandomBytes(ServiceCtx context)
         {
             byte[] randomBytes = new byte[context.Request.ReceiveBuff[0].Size];
 
@@ -23,7 +23,7 @@ namespace Ryujinx.HLE.HOS.Services.Spl
 
             context.Memory.WriteBytes(context.Request.ReceiveBuff[0].Position, randomBytes);
 
-            return 0;
+            return ResultCode.Success;
         }
 
         public void Dispose()