Implement memory control. #736
Description
This issue is used to track the flow control feature.
- Path-Level Flow Control *: implement basic flow control #733
- Area-Level Flow Control *: implement basic flow control #733
- Circuit Breaker Mechanism DS, eventCollector: drop event if needed #1430
- Add Integration test. DS, eventCollector: drop event if needed #1430
- Remove dropEvent to simplify memory control.