Remove choosePort and rely on dynamic, OS-allocated ports during tests

[ewencp]

[ewencp]

Works in conjunction with https://github.com/confluentinc/rest-utils/pull/90 and avoids Address already in use errors during tests due to choosePort not being a reliable way to select a random available port. Will probably need some work/follow up PRs to make it merge up through all recent branches, especially due to recent addition of Kafka-based coordination.

[cla-assistant[bot]]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}