More quality of service demo cleanup

[clalancette]

Based on the testing in https://github.com/osrf/ros2_test_cases/issues/783, this PR does further cleanup on the quality of service demos. There are 3 commits in here, to do the following things:

1. Make the teardown sequence in all of the Python examples the same. This means we won't throw an exception on shutdown in any of them anymore.
2. Make the output of the liveliness demos more consistent. For the Python one, print out object data rather than the reference, and for the C++ one have it use a logger.
3. Make the incompatible_qos python demo print out structure members.

[clalancette]

CI:

• Linux
• Linux-aarch64
• Windows

[clalancette]

Thank you!