Implement procctl flags and related structs:
struct target_procctl_reaper_status
struct target_procctl_reaper_pidinfo
struct target_procctl_reaper_pids
struct target_procctl_reaper_kill

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Karim Taha <kariem.taha2.7@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Warner Losh <imp@bsdimp.com>
Message-Id: <20230925182425.3163-3-kariem.taha2.7@gmail.com>