pgbouncer: use c-ares for name resolution (#66336)

According to pgbouncer README.md file c-ares is the
prefered way to resolve names for pgbouncer 1.10+:
https://github.com/pgbouncer/pgbouncer/blob/master/README.md#dns-lookup-support

The previous method (evdns) did not support EDNS0 and SOA lookups.