Add `--busy-timeout` command-line option to turso-stress with a default
value of 5000 ms. This helps prevent spurious database busy errors
during concurrent stress testing and ensure that integrity checks are
not skipped because of concurrent writes.
This adds a "limbo_stress" tool for stress testing Limbo in
non-deterministic way together with support code to run the tests under
Antithesis (which makes them deterministic). The stress tester does not
really do anything useful yet, this is just a step to make sure we can
run tests under Antithesis.
