[Async] (refactoring) Rename AnyEventTarget::GetImpl() to GetTargetImpl().
[Concurrent] Map and HashMap support Snapshot policy.
- Add ConstLockedMap and DictionarySnapshot classes.
[Concurrent] BasicMap add Erase() and Clear().
[Concurrent] BasicSet add Clear().
[Statechart] Verify all target states of transitions must exist when initating.
[Statechart] Change: StateMachine.Initiate() would trigger the initial state's enter action.