Add traceroute streaming parser - traceroute-s

[codeout]

This PR implements a traceroute streaming parser (see #576) and includes:

• A new streaming parser traceroute_s.py, which reuses most logic by delegating to traceroute.py.
• Refactors in traceroute.py to share classes/functions.
• Tests for traceroute_s.py, kept consistent with test_traceroute.py.

[kellyjonbrazil]

Looks great! Just a couple things above and I'll merge. I may also update traceroute.py with the new fields.