Streamline exception types

This patch reduces the number of exception types by facilitating
globally defined exceptions for common usage patterns shared by most
services. In particular, RPC functions that demand a session-resource
upgrade not longer reflect this condition via a session-specific
exception but via the 'Out_of_ram' or 'Out_of_caps' types.

Furthermore, the 'Parent::Service_denied', 'Parent::Unavailable',
'Root::Invalid_args', 'Root::Unavailable', 'Service::Invalid_args',
'Service::Unavailable', and 'Local_service::Factory::Denied' types have
been replaced by the single 'Service_denied' exception type defined in
'session/session.h'.

This consolidation eases the error handling (there are fewer exceptions
to handle), alleviates the need to convert exceptions along the
session-creation call chain, and avoids possible aliasing problems
(catching the wrong type with the same name but living in a different
scope).

repos/demo/include/launchpad/launchpad.h

@@ -199,7 +199,7 @@ class Launchpad_child : public Genode::Child_policy,
 				return *service;
 
 			Genode::warning(name(), ": service ", service_name, " not available");
-			throw Genode::Parent::Service_denied();
+			throw Genode::Service_denied();
 		}
 
 		void announce_service(Genode::Service::Name const &service_name) override