u-blox: implement IPv6 support
The u-blox modules like the TOBY-L210 have a good IPv6 implementation, we're just missing the corresponding bits in the ModemManager plugin to have the IPv6 connection working properly.
Attached logs from Thomas Schäfer testing the same.
Reference to the mailing list discussion: https://lists.freedesktop.org/archives/modemmanager-devel/2021-June/008665.html