Enable full tracing tests on ROS 2 CI

Actually declare a dependency on LTTng (liblttng-ust-dev and lttng-tools) so that tests can be run on ROS 2 CI.

• Enable starting a LTTng session daemon programmatically (instead of manually starting it https://gitlab.com/micro-ROS/ros_tracing/ros2_tracing/-/blob/35c8481b99914f952d99db84d7fbdee4f2199f43/.gitlab-ci.yml#L26) #72 (closed)
• Add/restore dependency on liblttng-ust-dev & lttng-tools for tracetools & tracetools_test !139 (closed)

Perhaps it would also be a good idea to label the tracing tests with tracing so that they can be skipped easily if needed, e.g.

set_tests_properties(test_<something> PROPERTIES
  LABELS "tracing"
)

Note: I think some time after the above^ was written, a helper macro was added to ament to do that