Move Connect / MM2 configuration preparation from the shell scripts to the operator

[scholzj]

Some time ago, we changed the way how we generate the configuration for Kafka brokers (and controllers) from it being done inside bash scripts in the container to have it done in the operator and share it via Config Map / Secret to the Pods which do only minimal changes to it (ideally none as #10656 tries to achieve). This leads to reduced footprint in the container image, improved test coverage (as the bash scripts are currently only tested in STs and have no unit tests).

I think this was a good change and we should try to continue in this direction with other operands - in particular Connect / MM2 next.

[ppatierno]

Triaged 03.10.2024: agreed on implementing this.