libnm: replace mac_address_blacklist type GArray with NMValueStrv

Summary

This replaces the underlying type of mac_address_blacklist, which is currently GArray, with a more re-usable NMValueStrv.

Purpose

This change allows us to implement mac_address_blacklist as a direct property.

Checklist

Please read https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/main/CONTRIBUTING.md before opening the merge request. In particular, check that:

• the subject for all commits is concise and explicative
• the message for all commits explains the reason for the change
• the source is properly formatted
• any relevant documentation is up to date
• you have added unit tests if applicable