How do we verify acknowledgement it the TCK?

[jroper]

The question is how do we verify message acknowledgement in the TCK? It's a reasonably fundamental feature of the spec, so important to verify, but there are a number of challenges:

1. Some messaging providers may only acknowledge every n messages, assuming idempotent messaging.
2. Some messaging providers may not retry on failure, rather they might send failed messages to a dead letter queue.

I think the second point there is actually not an issue. The messaging spec is a spec for handling messages as a stream. When handling messages as a stream, messages don't fail, the stream does. Any failure that comes from the stream may or may not be related to a particular message, but the stream doesn't and can't tell you that. When a failure occurs, all you have is an exception, and zero or more unacknowledged messages. And I'm pretty sure all queues that support acknowledgement can at least be run in a mode where messages are retried if the message is neither acked nor nacked.

As for message providers that only acknowledge every n messages, we could potentially require that the configuration for the TCK is n == 1, even if that's not the default.

[Emily-Jiang]

Port the tests from https://github.com/smallrye/smallrye-reactive-messaging/tree/master/smallrye-reactive-messaging-provider/src/test/java/io/smallrye/reactive/messaging/ack and remove the ones that depends on Mutiny or other tests only related to SmallRye.