Due to a bug in hardhat, the latest block timestamp was out of sync from the newHeads block timestamp which was causing some timing issues in the tests. To fix this, a compile flag, `codex_testing` (which was changed from `codex_enable_proof_failures`) is used to determine the bevhaviour of clock.now. If `codex_testing` is true, clock.now uses the latest block timestamp, else it uses the cached block.timestamp that was populated in the `newHeads` event.