Add support for setOauthbearerTokenRefreshCb in RdKafka implementation

[scorgn]

• Add oauthbearer_token_refresh_cb config value for setting setOauthbearerTokenRefreshCb

Support for sasl/oauthbearer was fully implemented into the php-rdkafka library today with the latest release which allows us to authenticate MSK through IAM . This is done through the setOauthbearerTokenRefreshCb method on the \RdKafka\Conf object. Unfortunately the kafka transport does not allow us to directly pass an already configured Conf object. This MR adds support through a configuration value.