Identifying overloaded engine when pooled runner is configured

[vijaynalawade]

Current behavior:
For pooled runner type, engine sets queue size based on FLOGO_RUNNER_QUEUE. Today, there is no way to find out that queue is full and all workers are busy. This could happen when trigger is receiving events faster and actions could not handle them. So, queue will fill up. After that, trigger event goroutines will be blocked on the queue channel until workers complete existing action and pick up new one.
Expected behavior:
At-least an API that can monitor current size of the queue and may generate alerts about the situation.
What is the motivation / use case for changing the behavior?
This can be leveraged for readiness probe in K8s. That would reduce incoming traffic to certain engine until adequate queue is available for further processing.
Additional information you deem important (e.g. I need this tomorrow):