Debug failed self-tests

[Luc45]

This PR aims to improve self-tests, which are failing randomly.

• It includes non-JSON text to the parallel process output (Any non-JSON output generated by the process running the test was previously discarded)
• It saves the JSON output (which is the result JSON) in a file and reads from the file instead
• It preserves output generated by the orchestrating process
• It uses a unique filename for result JSONs, which in rare cases could cause a race-condition
• It adds a --debug flag that shows all remote requests done (not enabled in CI for now)

This makes the self-tests more robust, and helps to debug it if it fails again.

Testing instructions

• Pull this branch
• Point your CLI to Prod
• Go to _tests directory and run php QITSelfTests.php run (Optionally add --debug)
• Wait for all tests to complete
• Assert all tests completes successfully

[Luc45]

I'll be going ahead and merging this to reduce PR review churn, since it's just related to self-tests, and the snapshots shows that there are no changes to results.