src: update cares_wrap OpenBSD defines

Move the `#define`s back into `cares_wrap.cc`, as they are part of
the implementation, not the declarations used in `cares_wrap.h`,
and apply the suggestion from
https://github.com/nodejs/node/pull/38572#discussion_r627809407
to make the defines a bit more generic and not check for OpenBSD
specifically.

Refs: https://github.com/nodejs/node/pull/38572

PR-URL: https://github.com/nodejs/node/pull/38670


Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>