Tests: Add Python test utils
Tests: Add "linking" ust regression test

Based on the "demo" test formerly part of lttng-ust.
Tests userspace tracing with directly, statically and dynamically linked
providers. Also meant as an exemple of building and tracing an application
with all types of provider linking.
Tests: Add "daemon" ust regression test

Based on the "daemon" test formerly part of lttng-ust.
Tests: Add "exit-fast" ust regression test

Based on the "exit-fast" test formerly part of lttng-ust.
Tests: Add "fork" ust regression test

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