After working on WT-6136, there are several follow-on testing enhancements for incremental backup that would be nice to have. Some items are:
1. test/csuite/incr_backup: Add a call to session->verify in check_table to verify the backed up table.
2. test/csuite/incr_backup: Add an enhancement to reproduce WT-6136, similar to test_backup15.py where, for every WT_BACKUP_RANGE block returned, we read in the previous version of the block and confirm that the current and previous versions differ.
3. test/suite/test_backup14.py and test/suite/test_backup15.py: There is a bug in those tests that prohibit calling self.add_data and self.session.checkpoint multiple times before taking an incremental. We should be able to add data and checkpoint many times between backups. This is an issue with the test as I've verified and confirmed that test_incr_backup does that same thing many times between backups.