tests: make auto-source-discovery-grouping test use sink.text.details

tests: make auto-source-discovery-grouping test use sink.text.details

This patch changes the way that test component classes for the auto
source discovery grouping CLI test reports the inputs passed to each
instantiated component.

Currently, they print to stdout the input names
in the components' __init__.  That is then check by the test script
(test_auto_source_discovery_grouping).  The
TraceCollectionMessageIterator class in the Python bindings will soon
have the capability to automatically discover source components.
However, it's not practical to use the same test method in Python.

To facilitate this, make the test component classes report the inputs
they receive by sending a stream beginning message, where the stream
name contains the input names.  The eventual Python test will be able to
inspect the stream name to validate that the right inputs were passed to
each component.

Since the information is now passed in messages, the
test_auto_source_discovery_grouping test now uses the details sink.

Change-Id: Ie5c12e390f5b68fb50a6d18c53463860fb7a1c99
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1863
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Tested-by: jenkins <jenkins@lttng.org>