feat: Add opa-tls functionality/opa integration test

[sbernauer]

Currently we don't have an integration test testing the OPA integration. The kafka-operator is also missing functionality to communicate with Opa over TLS.

Tasks:

• add a test with a simple (non-tls) opa configuration
• add tls-connectivity to opa from kafka
• test with kerberized kafka
• improve rego rule

[adwk67]

Release Notes snippet

Previously, Kafka supported OPA in non-TLS mode. Now both TLS and non-TLS modes are supported.
N.B. This is not yet supported by the Kafka Controller (available in Kafka 4.x).