Variable drain time when shutting down via shutdown API

[dlvenable]

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

When running Data Prepper, we sometimes we want to shutdown Data Prepper faster than it is configured for.

Presently, the Data Prepper shutdown process will wait for the buffers to drain.

buffer:
  kafka:
    drain_timeout: 30m

In some cases, we want to drain faster, say in 10 minutes.

Describe the solution you'd like

Update the shutdown API to allow for an alternate drain time.

curl -X POST http://localhost:4900/shutdown?drainTime=10m

[dlvenable]

Originally I proposed a drainTime parameter. However, there are multiple times involved currently. So instead of drainTime, I believe bufferReadTimeout and bufferDrainTimeout would be more appropriate.

The bufferReadTimeout will control how long to wait for the buffer to empty. This will control the run loop that is waits for the buffer to be completely empty. With a Kafka buffer, this may never happen.

The bufferDrainTimeout will override the Buffer:getDrainTimeout.