merge traceroute6 into traceroute

From: Lexi Winter <lexi_at_hemlock.eden.le-fay.org>
Date: Thu, 10 Apr 2025 17:19:21 UTC 
hello,

i have proposed a patch to merge traceroute6 into traceroute, so that
traceroute supports both IPv4 and IPv6 addresses:

https://github.com/freebsd/freebsd-src/pull/1647

jlduran@ has proposed an alternative approach to achieve the same thing
which is mentioned in the PR comments.

any feedback or review on this (with a view to getting it committed)
would be appreciated.

thank you in advance!