Describe the enhancement:
Bringing the Elastic Agent more in line with outputs supported by Beats.

Describe a specific use case for the enhancement or feature:
Enable customers who are using beats to send events/logs to a Kafka broker to be able to create the same environment and functionality using the Elastic Agent. Lack of this capability may be an inhibitor for the adoption of Elastic Agent.

Tasks to complete:

• Initial implementation Kafka Output #147
• Kafka output should support codecs #165
• Add an integration test for the Kafka output #166
• Kafka output topic selection should match that from beats output #167

Further related tasks

• Make Kerberos support GA for Kafka output #168
• Add "real" selector support for kafka output #203
• The shipper should report its output unit as DEGRADED when it cannot publish events to Kafka #230
• Performance test the shipper Kafka output #232