Renderer: Handle resize events on-demand instead of polling

We now differentiate between a resize event and surface change/destroyed
event, reducing the overhead for resizes in the Vulkan backend. It is
also now now safe to change the surface multiple times if the video thread
is lagging behind.

Source/Core/VideoBackends/Vulkan/Renderer.h

@@ -70,8 +70,6 @@ public:
   void SetViewport(float x, float y, float width, float height, float near_depth,
                    float far_depth) override;
 
-  void ChangeSurface(void* new_surface_handle) override;
-
 private:
   bool CreateSemaphores();
   void DestroySemaphores();
@@ -79,6 +77,7 @@ private:
   void BeginFrame();
 
   void CheckForSurfaceChange();
+  void CheckForSurfaceResize();
   void CheckForConfigChanges();
 
   void ResetSamplerStates();