[Feature] Show aggregated list of failures at conclusion of test

[chipzoller]

What would you like to be added:

Aggregate and display all test failures at the tail end of the CLI's report output.

Why is this needed:

With a large number of test cases, one has to scan the entire list of test results to understand which and where failures occur. Generally, test successes are expected and uninteresting--users primarily care about which tests fail. It should be a simple process to aggregate and display only the failures as the last portion of the CLI output.