Make File System view independent from ProjectExplorer

As preparation for moving it to Core so the "Show in File System View"
functionality can spread more.

Change-Id: I0f7d36f1d7eebe7b074c7949dd95b2cd985bfec8
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

src/plugins/coreplugin/coreicons.cpp

@@ -54,5 +54,9 @@ const Icon MODE_DESIGN_FLAT({
 const Icon MODE_DESIGN_FLAT_ACTIVE({
         {":/fancyactionbar/images/mode_design_mask.png", Theme::IconsModeDesignActiveColor}});
 
+const Icon DESKTOP_DEVICE_SMALL({{":/utils/images/desktopdevicesmall.png",
+                                  Theme::PanelTextColorDark}},
+                                Icon::Tint);
+
 } // namespace Icons
 } // namespace Core