Randomized testing of enforce_home_region

**Is your feature request related to a problem? Please describe.**
The enforce_home_region session setting relies on a Distribute operator being generated for all queries or query constructs (such as scalar expressions built from query expressions). To increase confidence that this operator is built in all necessary cases, randomized testing of enforce_home_region could be added.

**Describe the solution you'd like**
The best form of randomized testing is not known at this time. Maybe instrument the KV API to error out if it tries to access remote rows, or construct a Jepsen-like framework to prove no remote accesses occurred for a queries or sequence of SQL statements.

**Describe alternatives you've considered**
Brainstorming and manual testing to verify all constructs are covered, e.g. subqueries, cascades, apply join, etc.

**Additional context**
PR #102103 highlights a recent case where the Distribute operator failed to get generated when needed.

Jira issue: CRDB-27366
Epic: CRDB-34182