[Cosmos] add preferred regions logging

[simorenoh]

Adds the missing client config logs since this flag was the last bit missing for that. Logs look like this:

Progress towards closing #18986.

[simorenoh]

/azp run go - azcosmos - ci

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[jhendrixMSFT]

@benbp I think the ExcludeGoNMinus2 flag has regressed with the recent pipeline changes. It's set for azcosmos but is now showing up in CI.

[simorenoh]

@benbp - for context

with 1.21 in the go.mod file, these two runs complain of the lack of the min method:

with 1.22.0, the same two runs complain about the formatting:

It's only these two runs having issues - and previous PRs have already merged with the go.mod on 1.22.0:
#22394