citra_qt: Add Game List configuration

This adds a Game List configuration group box which is similar to yuzu's, with features including icon size setting, row 1/2 text, and ability to hide invalid titles (those without a valid SMDH). I also added a UI tab and moved the language and theme settings there.

src/citra_qt/game_list.h

@@ -62,6 +62,8 @@ public:
 
     QString FindGameByProgramID(u64 program_id);
 
+    void RefreshGameDirectory();
+
     static const QStringList supported_file_extensions;
 
 signals:
@@ -87,8 +89,6 @@ private:
     void ValidateEntry(const QModelIndex& item);
     void DonePopulating(QStringList watch_list);
 
-    void RefreshGameDirectory();
-
     void PopupContextMenu(const QPoint& menu_location);
     void AddGamePopup(QMenu& context_menu, const QString& path, u64 program_id, u64 extdata_id);
     void AddCustomDirPopup(QMenu& context_menu, QModelIndex selected);