redis: enable DNS lookups on redirections by default

[rgs1]

Once #23764 has been fixed and DNS lookups have been used heavily in deployments, it might be a good idea to have it on by default.

[phlax]

cc @mattklein123

[rgs1]

Pretty sure we should do this, the tricky part might be figuring out the dns_lookup_family until we get happy eyeballs support:

https://github.com/envoyproxy/envoy/blob/main/api/envoy/extensions/common/dynamic_forward_proxy/v3/dns_cache.proto#L56

I guess one way would be to have two caches (IPv4 and IPv6), and just try one after the other and then remember what succeeded for that host.

[rgs1]

If the default dns cache approach ends up being more complicated than necessary, we could fallback to making the dns_cache_config field mandatory (this might be API breakage, not sure what the policy for doing that is).

But this approach is certainly less error prone than trying to build a default DNS cache and guessing the IP settings, with the only downside of requiring more configuration.