VideoBackends: Combine Initialize/Prepare and Cleanup/Shutdown methods

Also allows the work previously done in Prepare to return a failure
status.

Source/Core/VideoBackends/OGL/Render.cpp

@@ -809,6 +809,7 @@ Renderer::~Renderer() = default;
 
 void Renderer::Shutdown()
 {
+  ::Renderer::Shutdown();
   g_framebuffer_manager.reset();
 
   UpdateActiveConfig();