benchmark: fix issues in dns benchmark

The benchmark script for dns contained functions with args declared
but never used. This fix removes those arguments from the function
signatures.

No test existed for the dns benchmark so one was added to the
parallel suite.
To improve performance the tests are limited to 1 invocation to a
single endpoint.

PR-URL: https://github.com/nodejs/node/pull/14936


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Refael Ackermann <refack@gmail.com>