LTTng: CPU usage analysis from the LTTng kernel trace

LTTng: CPU usage analysis from the LTTng kernel trace

This analysis creates a new state system to save the total time spent on each
CPU by the different threads. It then uses it, along with the LTTng kernel
state system to compute CPU usage statistics in a time range.

Change-Id: Ia60e95c3bace646477aef06d58bdb7ed64c32bd4
Signed-off-by: François Rajotte <francois.rajotte@polymtl.ca>
Reviewed-on: https://git.eclipse.org/r/21633
Tested-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Genevieve Bastien <gbastien+lttng@versatic.net>
Tested-by: Genevieve Bastien <gbastien+lttng@versatic.net>