xml: bug 497272 Populate views from built-in XML files

xml: bug 497272 Populate views from built-in XML files

This patch makes sure that outputs defined in built-in XML files
advertised through the extension point are added under their analyses.

It moves the method to list the built-in files from the analysis module
source to the XmlUtils class and adds a unit test for this use case.

Change-Id: I5984d1cc9adbbc7e6348632c0f58390f73db41bd
Signed-off-by: Geneviève Bastien <gbastien+lttng@versatic.net>
Reviewed-on: https://git.eclipse.org/r/78723
Reviewed-by: Jean-Christian Kouame <jean-christian.kouame@ericsson.com>
Tested-by: Jean-Christian Kouame <jean-christian.kouame@ericsson.com>
Reviewed-by: Hudson CI