Measure impact of sync trigger for partitioning migrations

The partitioning migration helpers use a trigger to write changes from the source table to the partitioned table. This trigger will remain in place until the migration is completed, and the application is fully cutover to the partitioned table. Before the migration is rolled out, measure the impact of the trigger as currently implemented.

The audit events table is append only, so the initial benchmark can focus on an INSERT/SELECT workload.