Execution Rate-limit policy

[zero88]

Is your feature request related to a problem? Please describe.

• In the case of EventTrigger, the event can be fired in massive in a short time
• In the case of Timing Trigger, the execution can be longer than the trigger period

Currently, schedulerx only allows running one job of a specified trigger in one moment. That is a limitation.
It is ideal to add a throttle mechanism to restrict the incoming event message for EventTrigger or in general, control the number of execution rounds of one trigger that can be run in parallel in a certain period.

Describe the solution you'd like
Provide the execution rate-limit policy interface, that

• Supports local memory counter
• Supports remote counter, such as the scheduler app is deployed on multiple instances in the cluster