Use uuid as first comparison criteria

Use uuid as first comparison criteria

This is most important in the message ordering reproducibility against
multiple sources where some might populate the trace name and some don't.

A good example of a source not populating the trace name is lttng-live.

It facilitates the testing of lttng-live source plugin since it is
possible to compare it to the src.ctf.fs plugin directly.

Philippe adds: there's a trace UUID property in a CTF metadata stream,
but no trace name property. The trace name is entirely up to the
specific CTF source component class. Therefore it's safer to use the
UUID to distinguish unique traces.

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Change-Id: I39f3c513e27bffd51ca02b089c097ac406e3316e
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1914
CI-Build: Philippe Proulx <eeppeliteloop@gmail.com>
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>