Custom KafkaPrincipalBuilder Cannot Access SslPrincipalMapper

When implementing a custom KafkaPrincipalBuilder, it is not possible to access SslPrincipalMapper and kerberosShortNamer. This limits the ability to parse Regex Rules from BrokerSecurityConfigs.SSL_PRINCIPAL_MAPPING_RULES_CONFIG, resulting in lack of support for Mapping Rules as SslPrincipalMapper is null.

A possible workaround is to read the configuration and build another SslPrincipalMapper. However, it would be beneficial if this issue could be addressed at the ChannelBuilders or SslChannelBuilder level.

Git Reference: https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/common/network/ChannelBuilders.java#L223-L242

If the community deems this to be a bug, I am willing to provide a fix.