VideoBackends:Metal: Bring back unified memory config

Turns out it was helpful.  (Most improvement in ubershaders.)  This time with much better auto mode.

Source/Core/VideoCommon/VideoConfig.cpp

@@ -55,6 +55,7 @@ void VideoConfig::Refresh()
 
   bVSync = Config::Get(Config::GFX_VSYNC);
   iAdapter = Config::Get(Config::GFX_ADAPTER);
+  iManuallyUploadBuffers = Config::Get(Config::GFX_MTL_MANUALLY_UPLOAD_BUFFERS);
 
   bWidescreenHack = Config::Get(Config::GFX_WIDESCREEN_HACK);
   aspect_mode = Config::Get(Config::GFX_ASPECT_RATIO);