Refactor using_default_dir_authorities() local address checks
Currently, we check for IPv4 and IPv6 local addresses and using_default_dir_authorities() in two different places:
- IPv4: resolve_my_address()
- IPv6: router_get_advertised_ipv6_or_ap()
Once we've combined the code that checks IPv4 and IPv6 advertised ORPorts, we can do a single using_default_dir_authorities() check.