Add initial paths to GameTracker after construction

It's strange to see GameTracker add its own initial paths in
construction, because you might expect a race condition where the
GameLoaded signal is emitted before it gets connected to in
GameListModel.

In fact, this doesn't happen, but only because of how it abuses the Qt
signals mechanism to load files asynchronously: GameLoader emits a
GameLoaded signal which gets forwarded to the GameTracker::GameLoaded
signal _after_ control returns to the event loop, at which point
GameListModel has connected.

This commit moves the logic of adding initial paths out of GameTracker
to a point after the signals are connected, which is more obvious and
doesn't rely on how GameTracker implements concurrency.

Source/Core/DolphinQt2/GameList/GameListModel.cpp

@@ -17,6 +17,9 @@ GameListModel::GameListModel(QObject* parent) : QAbstractTableModel(parent)
   connect(this, &GameListModel::DirectoryAdded, &m_tracker, &GameTracker::AddDirectory);
   connect(this, &GameListModel::DirectoryRemoved, &m_tracker, &GameTracker::RemoveDirectory);
 
+  for (const QString& dir : Settings::Instance().GetPaths())
+    m_tracker.AddDirectory(dir);
+
   connect(&Settings::Instance(), &Settings::ThemeChanged, [this] {
     // Tell the view to repaint. The signal 'dataChanged' also seems like it would work here, but
     // unfortunately it won't cause a repaint until the view is focused.

Source/Core/DolphinQt2/GameList/GameTracker.cpp

@@ -28,9 +28,6 @@ GameTracker::GameTracker(QObject* parent) : QFileSystemWatcher(parent)
   connect(m_loader, &GameLoader::GameLoaded, this, &GameTracker::GameLoaded);
 
   m_loader_thread.start();
-
-  for (QString dir : Settings::Instance().GetPaths())
-    AddDirectory(dir);
 }
 
 GameTracker::~GameTracker()