Expose buffer/size parameters for tracing

E.g. here: https://gitlab.com/micro-ROS/ros_tracing/ros2_tracing/blob/e585f0eefe64d79c7b6549d7db6984c5731d31f6/tracetools_trace/tracetools_trace/tools/lttng_impl.py#L99

If a lot of events are enabled, the current/default buffer size/setup can lead to events being discarded. Therefore, users should be able to set these parameters (or perhaps just the number of sub-buffers, i.e. n * 4096) to be able to avoid that.