dns: refactor internal/dns/promises.js

Use `isIP()` instead of `isIPv4()` since it does the additional
functionality that we were adding after our calls to `isIP()`.

This not-so-incidentally also increases code coverage from tests. At
least one of the replaced ternaries was difficult to cover reliably
because operating system/configuration variances were too unpredictable.

PR-URL: https://github.com/nodejs/node/pull/27081


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>