ctf: add tracer version extraction function

ctf: add tracer version extraction function

This commit adds a utility function to extract tracer version of a given
trace.

Because, it was discovered that some tracers may produce non-compliant
CTF traces more-or-less frequently. To accommodate those external tools,
we will add ad-hoc fixes for the affected version. We thus need a way to
check the tracer versions of the traces.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: I67e73a5928dfac0cebc1135552f5525af930ebfc
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1418
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>