Kroxylicious overlay

[tomncooper]

It would be good to have an overlay which includes the Kroxylicious Kafka Proxy. It has its own operator so should be able to be integrated into the base and stack kustomizations.

However, we might need to consider the best demo use-case for Kroxy. Just having it "there" connected to a single node kafka cluster is probably not very useful or compelling. We need to think about what is the minimum viable demo for Kroxy's functionality.

[Frawless]

In the past we used encryption example, oauth example and schema validation example - https://github.com/skodjob/deployment-hub/tree/main/streams/kroxylicious . As a store for keys for encryption scenario we use Hashicorp Vault which was pretty easy to install that time. I think we could double check if this is still possible and look for ephemeral version (HA one from examples requires unsealing of the vault during startup and only way how to make it automated was with external KMS store).