Add a correctness verification mode for tuple caching

To get more coverage of tuple caching correctness, it would be useful to have automated correctness checking for tuple caching. In this mode, the tuple cache node would fetch results from its child, persist the new results to disk, then compare the new results to the cache contents at the end. The goal is to be able to run a variety of queries, including various end-to-end tests and verify that there is no variability in the results stored to the cache.