Implement all agreed changes in CustomCaST 

CustomCaST

• testReplacingCustomClusterKeyPairToInvokeRenewalProcess
  • Improve/fix comments in this test suit, as it does not exactly reflect what is happening in the test. 
  • There is an open issue https://issues.redhat.com/browse/ENTMQST-4872 for dealing with situation when we remove old CA and private key, To look at when describing correctly. 
• testReplacingCustomClientsKeyPairToInvokeRenewalProcess
  • same case as previous test (testReplacingCustomClusterKeyPairToInvokeRenewalProcess) 
• testCustomClusterCACertificateRenew
  • this should be probably split into 2 tests (One test case for clientsCA, one for clusterCA).
  • extend test/s:
    • (Covered by current test case) -  Create CA with long validity - Configure Kafka with short server certs validty - Renew server certs and check that brokers uses new certs and CA is the same
    • (missing) - Create CA with some validity - Create Kafka with long server certs validity - Renew CA - CO should now roll all pods for clusterCa, for clients only Kafka pods -  (also Do not touch validity in Kafka CR directly)
• testClientsCaCertificateRenew
  • also create 2 test from this one. the same way as in previous i.e., one for clientsCA, one for clusterCA
  • extend test/s
    • already covered: Create CA with long validity - Configure Kafka with short server certs validty - Renew server certs and check that brokers uses new certs and CA is the same
    • missing: Create CA with some validity - Create Kafka with long server certs validity - Renew CA - CO should now roll all pods for clusterCa, for clients only Kafka pods -(Again Do not touch validity in Kafka CR directly)