Add Show in File System View to project tree context menu

That opens the selected file/path in the file system view.
Behaves the same as the navigation view shortcut + syncing with the
selected file.

It would be nice to have that at other places too, but this requires
moving the file system view to Core plugin first.

Change-Id: Icc6d1041156d97f5d2bda43a3501758f06fe80aa
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

src/plugins/coreplugin/fileutils.cpp

@@ -147,6 +147,11 @@ QString FileUtils::msgFindInDirectory()
     return QApplication::translate("Core::Internal", "Find in This Directory...");
 }
 
+QString FileUtils::msgFileSystemAction()
+{
+    return QApplication::translate("Core::Internal", "Show in File System View");
+}
+
 QString FileUtils::msgGraphicalShellAction()
 {
     if (HostOsInfo::isWindowsHost())