Support early draining

[v0idpwn]

We can't guarantee that the application won't generate stuck messages to be saved by the rescuer, but we can make a best effort:

1. Stop producing messages when the application begins to shutdown
2. Hold the shutdown for a maximum amount of seconds in an attempt to drain the publisher and the acknowledger

[v0idpwn]

(2) is already done through Kafkaesque.Pipeline. (1) can be added as an optional process to be added in the supervision tree.