Provide access to correlated IN-/OUT-Messages

**User story**
As a tester I would like to have detailed information on my test execution. Very important information are the messages send and received during execution. I want to be able to define whether I want to see the details on each test case or only on failed test cases.

As a deveoper extending the Citrus framework, I want to be able to create a TestReporter that can access all Messages send/received during test execution.

No files, tests, or entry points are named in the issue. Start by locating the test execution and TestReporter extension points, then trace how sent and received messages are handled; done should provide correlated messages and allow details to be shown for every test case or only failed cases.

Written by the indexing model from the issue text.