Although a small multi-threaded test was added in test_tiered08.py in the python test suite in WT-7701 and WT-7754, we also want a stress test similar to csuite/timestamp_abort that randomizes a lot of operations.

Some thoughts:

• Use timestamp_abort as a basis because we want to test using operations that mimic MongoDB as much as possible. So having the timestamp usage and prepared transactions comes for free.
• Add a flush_tier thread too. Some ideas for this new thread are to have it just randomly sleep and call flush_tier periodically. Or have each iteration wait a random-N (small N, probably 1:5) checkpoints between flush_tier calls.
• Have the timeout start counting after N flush_tier operations have completed. Right now the timer starts after the first checkpoint completes.
• Possibly add in testing multiple databases running to the same local bucket with different prefixes. This would be a stretch goal but desirable to get testing sooner than later.