Alternate addresses are always used if defined instead of applying heuristic

Similar to MB-37626, we need to be a bit more intelligent in when we use the alternate addresses configured on the cluster.

If a remote cluster has an external address set, then when SG connects it will always use the external address.

This is in contrast to the SDKs where they select which address (default vs external) based on the node that you initially connect to.

SG should behave in the same way, as there's no guarantee that SG can access the external hostname ports, even if they are set for other clients to access.
If you specify the Couchbase Server cluster with the external hostname (i.e. it's present in the external address section of the node info), then it should use the external address, otherwise it should use the default address/ports.