tmf.core: make Analyses with experiments add children analyses when available.

tmf.core: make Analyses with experiments add children analyses when available.

This is a feature that allows experiments to use the analyses of their children.
The analyses are in a list so that the parent trace is always the first one.

Change-Id: I0f6ba6d38fecb49e4575bd0a4dd1d8602970f4d6
Signed-off-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/71100
Reviewed-by: Hudson CI
Reviewed-by: Genevieve Bastien <gbastien+lttng@versatic.net>
Tested-by: Genevieve Bastien <gbastien+lttng@versatic.net>