Fail the test Pipeline if <N test results are reported

[kmahone]

We report test results from Helix into Azure Pipelines. If a test fails it should show up in the build test report and the build will show as failed.

However, if something goes wrong and something prevents the results from being reported, we might not notice that some results are missing from the build.

It would be nice if we have some extra step in the Pipeline that did something like "If less than 700 test results were reported then fail the build with an error". This would convert "absence of evidence" to "evidence of absence".

I don't think there is any existing feature that we can use for this, but we might be able to create something via the REST api: https://docs.microsoft.com/en-us/rest/api/azure/devops/test/results/list?view=azure-devops-rest-5.0