* Add contrib/debug_determinism
Add an instrumentation-based technique for debugging unseen mismatches. Also guard a few existing sources of nondeterminism that don't affect unseen with the DEBUG_DETERMINISM macro.
Also change the simulated run loop to not run as the only task inside the real run loop, since that was a source of nondeterminism.
Also fix nondeterminism from calling timer_int
* Add StorageMetadataType::currentTime
Basically a deterministic-in-simulation version of timer_int that we can
use instead of timer_int for StorageMetadataType::createdTime
Jingyu Zhou