Replace get_configured_ip_addresses() and get_configured_ipv6_addresses() with a more pragmatic approach, both are used to detect if an address is already configured, which gets quite sloppy when having a large number of interface
s configured.

This change probes all configured interfaces at once, and returns the full list, stripping quite some magic in the process.

Because the indexing is changed, we need to change the consumers as well here.