sql: collect log-based telemetry on regions visited by each query

[rytaft]

Is your feature request related to a problem? Please describe.
Currently our log-based telemetry does not include the regions visited by a query. It would be helpful to know how many of our customers' queries are visiting multiple regions.

Describe the solution you'd like
The log-based telemetry should include all the regions visited by a query, similar to the region information currently output by EXPLAIN ANALYZE. Although the EXPLAIN ANALYZE output today doesn't technically include every region touched by the query (e.g., if the KV api fetches data from a remote region this will not be represented), it will give us a pretty good idea. In particular, it will include all the regions where DistSQL processors are planned.

Describe alternatives you've considered
It would be helpful to include regions visited by the KV api, but this would be a more invasive change.

Jira issue: CRDB-18243

[rytaft]

cc @awoods187

[awoods187]

cc @vy-ton for awareness as I'm out