[CT-2922] Produce unit testing artifacts for metadata about unit testing

[gshank]

Description

We should produce json artifacts which can be ingested and used as metadata about unit testing. There will be at least two types of artifacts, including a "result" artifact and a more manifest-like artifact.

The output in the run_result should organize test output by the unique_id of the model that they're running on, should include test result output, and a lightweight unit test structure.

Developing these artifacts will require settling on a "node-like" representation of unit tests, which will resemble the unparsed yaml objects, but have some additional data, but will not include everything in the UnitTestNode object.

Acceptance criteria

We should have a run result structure and an artifact structure that we can share with other teams for feedback.

[gshank]

Merged into unit testing feature branch with #8477