qapi stats: Elide redundant has_FOO in generated C

qapi stats: 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/stats.json.

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

Cc: Mark Kanda <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Signed-off-by: Markus Armbruster <[email protected]>
Reviewed-by: Mark Kanda <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Message-Id: <20221104160712.3005652[email protected]>