VideoConfig: Prevent race condition on g_Config when refreshing

There was a race condition between the video thread and the host thread,
if corrections need to be made by VerifyValidity(). Briefly, the config
will contain invalid values. Instead, pause emulation first, which will
flush the video thread, update the config and correct it, then resume
emulation, after which the video thread will detect the config has
changed and act accordingly.

Source/Core/VideoCommon/MainBase.cpp

@@ -192,7 +192,6 @@ void VideoBackendBase::InitializeShared()
 
   g_Config.Refresh();
   g_Config.UpdateProjectionHack();
-  g_Config.VerifyValidity();
   UpdateActiveConfig();
 }