tests: test removing a destruction listener from a destruction listener

tests: test removing a destruction listener from a destruction listener

This patch adds a test to verify that removing a trace or trace class
destruction listener from an object from within a destruction listener
of that same object works correctly.

It tests 3 scenarions:

- A destruction listener removing itself.
- A destruction listener removing a destruction listener that was
  already called.
- A destruction listener removing a destruction listener that is not yet
  called.

This assumes that destruction listeners are called in the order in which
there were added.

In the third scenario (removing a destruction listener that is not yet
called), the result is that the removed listener won't get called.

Change-Id: I49de9b662b3c1f77ca1c9f84c2c3575a8616cc10
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/2429
Tested-by: jenkins <jenkins@lttng.org>