Add validation for all immutable KafkaSpec fields while Kafka resource update

[testisnullus]

We can update only specified fields inside the KafkaDataCentre array. For now, we don't have validation for all KafkaSpec fields, so customers can easily try to update them. We need to add validation for these fields to prevent such kinds of actions.

Please check the doc - https://instaclustr.redoc.ly/Current/tag/Apache-Kafka-Provisioning-V2#paths/~1cluster-management~1v2~1resources~1applications~1kafka~1clusters~1v2~1%7BclusterId%7D/get and add validation for fields that cannot be updated.