Devoncarew fix test runner

Fix the test runner locally. We changed jobs to only allow one to run at a time. This changes our test runner to not run as a job. Tests now run locally (`dart tool/test_runner.dart --dartium` and `dart tool/test_runner.dart --chrome`). They still fail on the bots. Not sure why.

@ussuri, @umop

If this looks good, can somebody please merge it. We'll then need to look at why the tests don't start on the bots.