Tests: Add Python test_utils module

Basic Python test framework based on the lttng-tools Python bindings
that facilitates the creation of a tracing session saving its trace in
a temporary location, the activation of events in the UST domain and
clean teardown of the test session.

Also provides basic TAP output facilities.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>