Cluster_V4_ONLY cause `no healthy upstream` on IPv6 first cluster

xref: https://github.com/envoyproxy/gateway/issues/4572

https://github.com/envoyproxy/gateway/blob/05817fcc42d803caba384d54eee6d9f0c562c1ef/internal/xds/translator/cluster.go#L87

should we change to auto by default?

cc @arkodg @juwon8891 