Expose Assertion Count to Jenkins

It is possible on the PIFR bots to have two consecutive tests that improve the assertion count, yet have the same number of failed test methods. Without displaying that level of granularity, an improvement from patch to patch might not be visible: E.g.:

https://www.drupal.org/node/2476947#comment-10322637 #133 and #134 had 10 and 7 respectively, yet the same two test methods failed.

Exposing this information to the developers should provide more granular information, and is therefore valuable.

This information is already tracked here: http://cgit.drupalcode.org/drupalci_testbot/tree/src/DrupalCI/Plugin/Bui...

It needs to be put into the xml somewhere where jenkins can find it.
The only place I can see is in the testsuite properties - meaning that d.o. would need to aggregate those groups.

e.g.

<testsuite>
<properties>
  <property name="Passing Assertions" value="22" />
  <property name="Failing Assertions" value="7" />
</properties>
etc etc
</testsuite>