We should assert MVCC stats in roachtests, by enabling the following environment variables:

• COCKROACH_CONSISTENCY_AGGRESSIVE=true
• COCKROACH_ENFORCE_CONSISTENT_STATS=true

This will perform synchronous consistency checks after certain operations, and crash the node if any MVCC stats are incorrect when compared to the real data.

This may surface latent stats issues, so we should be prepared to clean these up.

Jira issue: CRDB-18854