We're adding persisted statistics to allow developers to see trends in query performance over time using our internal tables and the DB console. We should augment these views with a way to allow developers to easily detect query plan changes over time.

For initial detection, we should introduce some hash or unique identifier for each plan. The developer should then be able to quickly view the plans themselves and understand what the specific change was.

Tracking plan hash item:
Epic: CRDB-6564

Jira issue: CRDB-8575