[DOC OCP, RHEL] Document Kafka Bridge enhancements for AMQ Streams 1.6

The recent upstream releases of Strimzi Kafka Bridge contain the following enhancements:

• Add topic/partition retrieval endpoint (Bridge version 0.18.0)
• Rename HTTP Server and Consumer and Producer metrics using strimzi_bridge prefix (Bridge version 0.18.0) - NO DOC CHANGES ARE NEEDED FOR THIS ENHANCEMENT
• Add support for Kafka headers on records / messages (Bridge version 0.19.0)

These enhancements should be described in the AMQ Streams documentation for the Kafka Bridge.

We should also update the Streams 1.6 Release Notes for both OpenShift and RHEL.