XML report: add file and line number

[gforcada]

Whenever zope.testrunner generates an junit XML test report it would be great if it also reports the file name and the line, like:

https://github.com/mikepenz/action-junit-report/blob/main/test_results/xunit/report.xml

This way, GHA like https://github.com/mikepenz/action-junit-report would be able to annotate a PR diff view with the test failures 🎉 making it much more obvious and efficient to see which tests did fail and what's the traceback 🌟