yuzu: Implement Vulkan frontend

Adds a Qt and SDL2 frontend for Vulkan. It also finishes the missing
bits on Vulkan initialization.

src/yuzu/main.h

@@ -130,7 +130,6 @@ private:
     void PreventOSSleep();
     void AllowOSSleep();
 
-    QStringList GetUnsupportedGLExtensions();
     bool LoadROM(const QString& filename);
     void BootGame(const QString& filename);
     void ShutdownGame();