Write a proper rmw_take_sequence test

[clalancette]

While investigating the causes behind ros2/rmw_cyclonedds#279 , we discovered that there is no test within ROS 2 that actually does a rmw_take_sequence and then checks on the results. We do have a test that is pretty close: https://github.com/ros2/rcl/blob/7a25a74cf911840224fb5b992d118c22c825f961/rcl/test/rcl/test_subscription.cpp#L388 . That initializes the sequence, fills it with messages, and then calls rcl_take_sequence.

It would be nice to have another variant of this test in this repository which specifically deals with rmw_take_sequence.