test: move dns test to test/internet

parallel/test-dns-cares-domains needs a working internet connection
to function (or a local DNS resolver that returns an answer quickly),
otherwise it times out.  Move it to test/internet.

PR-URL: #5905
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: James M Snell <[email protected]>

Author: bnoordhuis