timing.core: Add local statistics to the latency statistics

Add the local statistics in the statistics view and update the general
item tree of the view. The SystemCallLatencyStatisticsTableAnalysisTest
is updated in consequence.

Change-Id: I5209f9c6430ee4658e3cf55ef50f4769b8e28772
Signed-off-by: Jean-Christian Kouame <jean-christian.kouame@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/80952
Reviewed-by: Genevieve Bastien <gbastien+lttng@versatic.net>
Tested-by: Genevieve Bastien <gbastien+lttng@versatic.net>
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>