Fix DumpCommand to generate html with/out sandbox

api:doc:dump --format=html always disables the Sandbox since the check in DumpCommand seems to be wrong. There is always an option called "no-sandbox" and so irrespective of what you feed in the command line, the setEnableSandbox is set to False.

Fixed that as well as introduce a dummy Request Object as the layout.html.twig expects an app.request object. Otherwise it fails with a "You cannot create a service ("request") of an inactive scope ("request")."