Fix/resolve flaky error in tests

Release notes

[rn:skip]

Fixes some flaky test acting on 3 things:

drop from custom low level client the callback mechanism and the queue, but resort just in the queued messages an wait blocking on it.
updates the Publish collect based on Paho client to release the latch only after having copied the data, to avoid nulls due to read ordering From
```
latch.countDown();
receivedTopic = topic;
receivedMessage = message;
```
to
```
receivedTopic = topic;
receivedMessage = message;
latch.countDown();
```
in HiveMQ client usages, register the listener to subscribe before the verification and not during the verification. This makes the code less linear, but it's the intended use of the API.