fuzz: Simplify how we compute available machines and types

fuzz: Simplify how we compute available machines and types

apply_to_qlist(), apply_to_node() work with QObjects.  This is
designed for use by tests/qtest/qos-test.c, which gets the data in
that form via QMP.  Goes back to commit fc281c8020 "tests: qgraph API
for the qtest driver framework".

Commit 275ab39d86 "fuzz: add support for qos-assisted fuzz targets"
added another user: qtest/fuzz/qos_fuzz.c.  To get the data as
QObjects, it uses qmp_marshal_query_machines() and
qmp_marshal_qom_list_types().

All this code is rather cumbersome.  Switch to working with generated
QAPI types instead:

* Replace apply_to_qlist() & friends by machines_apply_to_node() and
  types_apply_to_node().

* Have qos_fuzz.c use qmp_query_machines() and qmp_qom_list_types()
  instead.

* Have qos_test.c convert from QObject to the QAPI types.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20200424071142.3525-3-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Alexander Bulekov <alxndr@bu.edu>