timing library Null safety
- Track all async execution as disjoint time slices in ascending order.
- No-op implementation of SyncTimeTracker that does nothing.
- Async actions returning Future will be tracked as single sync time span from the beginning of execution till completion of future
- Tracks only sync actions
- The timings of an operation, including its startTime, stopTime, and duration.
- The timings of an async operation, consist of several sync slices and includes total startTime, stopTime, and duration.