Add detection of debugfs and kernel module loading

Add detection of debugfs and kernel module loading

The session daemon now detects the path of the debugfs mount point or
create and mount it at a default location (/mnt/debugfs).

Then, the kernel module are loaded automatically, if present, and the
kernel tracer fd is opened at the previous detected debugfs path.

The kernel module list is hardcoded for now.

NOTE: There is no module unload at the session daemon cleanup. This is
to avoid removing tracing capabilities when a trace is ongoing and
written to disk.

Signed-off-by: David Goulet <david.goulet@polymtl.ca>