Use PEM certificates loaded from secrets for MirrorMaker2

[tinaselenge]

Type of change

Select the type of your PR

• Refactoring

Description

• Use TLS certificates in PEM format directly using KubernetesSecretConfigProvider when configuring MM2 connector.
• Copy source and target's clusters trusted certs secrets into a single internal secret and then use key pattern (*.crt) of KubernetesSecretConfigProvider to load multiple certificates for ssl.truststore.certificates configuration.
• Remove scripts used for preparing PKCS12 files as no longer need.
• Remove generation of environment variables used by the scripts that are removed.
• Remove volumes and volume mounts used for ssl keystore and truststore, as they are now loaded from secrets directly.
• OAuth truststore is however configured differently, because multiline line certificates in Jaas config is not parsed correctly. Instead it will copy all the trusted certificates in PEM format into an internal secret under a single key and then volume mount it to use for ssl.truststore.location of oauth configuration.

Resolves part of #11294

Checklist

Please go through this checklist and make sure all applicable tasks have been done

• Write tests
• Make sure all tests pass
• Update documentation
• Check RBAC rights for Kubernetes / OpenShift roles
• Try your changes from Pod inside your Kubernetes and OpenShift cluster, not just locally
• Reference relevant issue(s) and close them after merging
• Update CHANGELOG.md
• Supply screenshots for visual changes, such as Grafana dashboards

[tinaselenge]

We no longer this script because this script prepared PKCS files and then ran kafka_connect_run.sh. Since preparation of PKCS files is removed, we just need to run kafka_connect_run.sh set in container config.