Add multicast options to ros2 doctor hello

[Miko997]

Description

Add optional --group and --port arguments to ros2 doctor hello. The selected values are used by the multicast sender and receiver and shown in the summary. Existing defaults remain unchanged.

This implements the multicast configuration part of #1077. The other enhancements in that issue are outside this PR.

Is this user-facing behavior change?

Yes. Users can select the multicast group and port used by ros2 doctor hello.

Additional Information

Post-review validation:

• git diff --check origin/rolling...HEAD
• python3 -m py_compile ros2doctor/ros2doctor/verb/hello.py ros2doctor/test/test_cli.py
• focused argument validation accepted 225.0.0.2 and rejected 127.0.0.1, not-an-address, and ff02::1
• ament_flake8 and ament_pep257 passed on the changed files

The full ROS 2 package test suite was not rerun after the review update.

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[fujitatomoya]

Pulls: #1267
Gist: https://gist.githubusercontent.com/fujitatomoya/d1427c44471cf6bf77af1c65fdbe2361/raw/4dee95e32e013daa3755a7f14c74fe197b4dc390/ros2.repos
BUILD args: --packages-above-and-dependencies ros2doctor
TEST args: --packages-above ros2doctor
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/20224

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[ahcorde]

@fujitatomoya should we backport this one ?