connect: built-in proxy/SDK should use ?cached service discovery

[banks]

In 1.3.0 we added ?cached queries for service discovery. The whole reason for adding these was to enable built-in proxy (and other proxy implementations) to "fail static" such that they can still make outbound requests during a partition from the servers or server outage.

Envoy is unaffected since it requires that we "push" the results to it so it's inherently static, Using ?cached in the SDK is a trivial change that will let built-in proxy and native apps have the same behaviour without having to support full load balancing decisions locally.