Add support for Ultralytics Yolo tracking format

[gboeer]

With newer yolo models by Ultralytics it is possible to perform object tracking.
Currently, it is not possible to handle such tracking outputs with datumaro.

In particular, the output of Yolo can contain a tracking id for each bounding box like:
<class_id> <x_center> <y_center> <width> <height> <track_id>

It would be good to be able to load such datasets and especially to convert them to other dataset formats which allow having a tracking id as well.

[jihyeonyi]

Thanks for your interest in datumaro project.
We will consider supporting the new format.