Summary

WT-18878 checks transaction commit and durable timestamps against the last checkpoint pickup timestamp on the follower in disaggreated storage. The prepare timestamp should be checked against the same checkpoint timestamp when a transaction is prepared on a follower.

Expected behavior

A transaction should not be allowed to prepare with a prepare timestamp at or below the last checkpoint pickup timestamp. Add validation for the prepare timestamp so prepare-time validation preserves the checkpoint timestamp invariant enforced for commit and durable timestamps.

Related issue

WT-18878