qapi machine: Elide redundant has_FOO in generated C

qapi machine: Elide redundant has_FOO in generated C

The has_FOO for pointer-valued FOO are redundant, except for arrays.
They are also a nuisance to work with.  Recent commit "qapi: Start to
elide redundant has_FOO in generated C" provided the means to elide
them step by step.  This is the step for qapi/machine*.json.

Said commit explains the transformation in more detail.  The invariant
violations mentioned there do not occur here.

Cc: Eduardo Habkost <eduardo@habkost.net>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Cc: Yanan Wang <wangyanan55@huawei.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20221104160712.3005652-16-armbru@redhat.com>