Fix Py_BuildValue / PyArg_ParseTuple format codes that don't match the C argument types (#3021)

Follow-up to #3019. With Claude, I audited every `Py_BuildValue` and
`PyArg_ParseTuple` call in the C tree against the real system headers
and fixed the mismatches, one commit per platform.

Plainly wrong values: `net_io_counters()` on 32-bit BSD,
`Process.uids()/gids()` on 32-bit AIX, and `Process.uids()/gids()` on
SunOS returning negative ephemeral ids. All of these were bugs, meaning
they returned wrong values on 32-bit platforms.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>