net: port isIPv6 to JS

Porting isIPv6() to JS makes it 10%-250% faster in most cases and
reduces some C++ code. This change also adds tests for some edge
cases.

PR-URL: https://github.com/nodejs/node/pull/22673


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Roman Reiss <me@silverwind.io>