What I did

Add support for test files that do not use a describe block (aka "flat") to the junit-reporter.

A file like this would now be included in the report, where before it would not:

it('under addition', function () {
  chai.expect(1 + 1).to.equal(2);
});

it('null hypothesis', function () {
  chai.expect(true).to.be.true;
});

it('asserts error', function () {
  chai.expect(false).to.be.true;
});

As for what to call the Test Suite - I followed the same pattern that the toResultsWithMetadataByBrowserTestFileName function was using. So each of these test suites will be named based on the browser + file being tested.

This should be a non-breaking change from my testing - it is only intended to detect some test cases that wouldn't be included previously!

closes #2901