Tests: Add the tracefile size test

This test validate the newly introduced tracefile count feature.  In
order to so, we enable a channel with the appropriate file size limits.

After running an instrumented application, we validate that each file in
the trace folder is no larger than the limit set on the command line and
also that some events are present (it's possible that the tracer discard
events, so we can't validate on a fixed number of events in the
resulting trace).

Signed-off-by: Christian Babeux <christian.babeux@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>