We update the stats for timestamps and transaction ids written in __rec_page_time_stats. However, it always assumes a full page is written. Therefore, the stats is wrong when we actually write a delta. Fix the stats to consider delta.

Right now, the stats are now double counted for keys that we write a delta as currently we always build a full disk image in reconciliation.

After fixing this, there is no need to turn off the leaf delta config in test_checkpoint09 test.