Added Disabled flag to Achievement Manager

The Disabled state sits between Game Closed and completely Shutdown - stronger than the former, as it refuses to let a game be opened again until AchievementManager is restored (which only happens upon a fresh core boot) but it isn't completely shut down and will still allow the player to be logged in and access the achievement settings and their (global) achievement header.

Source/Core/DolphinQt/Achievements/AchievementHeaderWidget.h

@@ -30,6 +30,7 @@ private:
   QProgressBar* m_game_progress_hard;
   QProgressBar* m_game_progress_soft;
   QLabel* m_rich_presence;
+  QLabel* m_locked_warning;
   QGroupBox* m_header_box;
 };