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.
Add "daemon" ust regression test

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

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