Core/Movie: Refactor to class, move to System.

A bit of global state remains (the `header` in `BeginRecordingInput()`) due to unclear lifetime requirements.

Source/Core/VideoCommon/VideoConfig.cpp

@@ -47,8 +47,9 @@ static bool IsVSyncActive(bool enabled)
 
 void UpdateActiveConfig()
 {
-  if (Movie::IsPlayingInput() && Movie::IsConfigSaved())
-    Movie::SetGraphicsConfig();
+  auto& movie = Core::System::GetInstance().GetMovie();
+  if (movie.IsPlayingInput() && movie.IsConfigSaved())
+    movie.SetGraphicsConfig();
   g_ActiveConfig = g_Config;
   g_ActiveConfig.bVSyncActive = IsVSyncActive(g_ActiveConfig.bVSync);
 }