Move File System view to Core plugin

So it can be accessed from a wider range of places.

Change-Id: I282883addecf7bb070a65d9f4f7b8e6e2e4b5e47
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/coreplugin/coreplugin.cpp

@@ -26,6 +26,7 @@
 #include "coreplugin.h"
 #include "designmode.h"
 #include "editmode.h"
+#include "foldernavigationwidget.h"
 #include "helpmanager.h"
 #include "icore.h"
 #include "idocument.h"
@@ -104,6 +105,7 @@ CorePlugin::~CorePlugin()
     Find::destroy();
 
     delete m_locator;
+    delete m_folderNavigationWidgetFactory;
     delete m_editMode;
 
     DesignMode::destroyModeIfRequired();
@@ -176,6 +178,8 @@ bool CorePlugin::initialize(const QStringList &arguments, QString *errorMessage)
     m_editMode = new EditMode;
     ModeManager::activateMode(m_editMode->id());
 
+    m_folderNavigationWidgetFactory = new FolderNavigationWidgetFactory;
+
     IWizardFactory::initialize();
 
     // Make sure we respect the process's umask when creating new files