Tests: Add "exit-fast" ust regression test

Based on the "exit-fast" test formerly part of lttng-ust.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Tests: Add "fork" ust regression test

Based on the "fork" test formerly part of lttng-ust.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Tests: Add "libc-wrapper" ust regression test

Based on the "test-libustinstr-malloc" test formerly part of lttng-ust.

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