Rename router_get_advertised_*() functions.

These now (or_port and dir_port) now have "find" names, since they
look at the portcfg first, then at the actual ports from the
listeners.

This is an automated commit, generated by this command:

./scripts/maint/rename_c_identifier.py \
        router_get_advertised_or_port routerconf_find_or_port \
        router_get_advertised_ipv6_or_ap routerconf_find_ipv6_or_ap \
        router_has_advertised_ipv6_orport routerconf_has_ipv6_orport \
        router_get_advertised_dir_port routerconf_find_dir_port