gitlab-ci: Enable unit test reports for traces jobs
Enhance tracie to produce JUnit XML files which gitlab CI can process and produce gitlab unit test report.
An example of the report produced (with some purposefully broken traces replays):
https://gitlab.freedesktop.org/afrantzis/mesa/-/pipelines/198261/test_report
Tracie producing the JUnit XML itself may become irrelevant when the WIP piglit integration arrives, but, until then, we can have a report that's easier for developers to read, with direct links to the dashboard image diff in case of failure.