The json test results format supports artifacts now. We should try to surface these in SOM for sheriffs. https://chromium.googlesource.com/chromium/src/+/master/docs/testing/json_test_results_format.md#per_test-fields roughly documents the format.

I had ideas about how to do this; I feel like joanna did some work with test results that we could add artifact information to? I'm not sure if that landed at all though.