In #95449, we began populating a regions field in the statement_statistics tables to provide a stable historical view of the regions in which a statement was executed.

The frontend code currently derives regions at view time from the sibling nodeIDs field and a call to the /_status/nodes endpoint, which is insufficient for serverless given the ephemeral nature of the nodes. (That is, /_status/nodes will only return current, not historical, nodes; and node IDs can technically disappear from one region and reappear in another.)

The frontend code should instead remove all usages of the nodeRegionsById selector (and any unused supporting code) and switch to simply reading this new regions field.

This is important for correctness when 23.1 is released to serverless, and I've been considering it a GA blocker for 23.1.

Jira issue: CRDB-25053