The upgrade/downgrade tests contains methods, that are not needed anymore or are a bit confusing. Also, the steps in each tests are a bit confusing, it would help to write down some JavaDoc that will help with understanding particular scenario.

In Strimzi#9442 there was a small clean up of methods for KRaft to KRaft upgrades/downgrades, we should do something similar for the regular upgrade/downgrade as well.

Another thing is unused or confusing fields of the upgrade/downgrade YAML files.

And finally, we should go through the OLM upgrade scenario and make sure that it is in some way similar to the bundle tests -> at least in terms of scenario.