Describe the problem

For #59680, we should add a multi-region roachtest.

I'm uncertain about the specific assertions this roachtest could make, given our focus on a best-effort approach and the need to balance NotLeaseHolder errors v.s. long write latencies. However, the test could potentially validate that the policies are being correctly applied somehow.

This issue can serve as a placeholder to track that effort.

• Extend policy_refresher_test.go with a mocked out latency map. done in kvserver/closedts: add TestPolicyRefresherWithLatencies #144482.
• Add a test for the race condition we were worried about https://reviewable.io/reviews/cockroachdb/cockroach/142721#-ONKsU7WCKoy8IrrX8hq. Done in kvserver: add mixed version race condition test for policy refresher #144106.

Jira issue: CRDB-49142