feat(ipinfo): accept multiple fields

[Komzpa]

Summary

• accept comma-separated --ipinfo field lists such as --ipinfo 0,1
• print the selected fields together in curses/report-wide host prefixes
• keep interactive y/z cycling compatible by collapsing back to a single selected field
• add command-line parser coverage for valid and malformed field lists, including non-numeric entries
• report malformed entries as ipinfo parser errors instead of a generic invalid argument

Fixes #201.

Inspired by the multiple-ipinfo behavior shown by yvs2014 in https://github.com/yvs2014/mtr085. This is a fresh implementation for the current upstream ui/asn.c code path rather than a cherry-pick from that fork.

Tests

• git diff --check
• make -j$(nproc)
• sudo python3 ./test/cmdparse.py
• ./mtr --ipinfo 0,1 --help
• ./mtr --ipinfo 0,,1 --help exits non-zero with an ipinfo parser error
• ./mtr --ipinfo 0,x --help exits non-zero with an ipinfo parser error