KAFKA-18293 Remove org.apache.kafka.common.security.oauthbearer.secured.OAuthBearerLoginCallbackHandler and org.apache.kafka.common.security.oauthbearer.secured.OAuthBearerValidatorCallbackHandler

KAFKA-18293 Remove org.apache.kafka.common.security.oauthbearer.secured.OAuthBearerLoginCallbackHandler and org.apache.kafka.common.security.oauthbearer.secured.OAuthBearerValidatorCallbackHandler #6858