Step tools to help debug failing steps

Copy paste of Behat\Testwork\Tester\Runtime\RuntimeSuiteTester which is a final class

Copy paste of Behat\Behat\Output\Statistics\TotalStatistics which is a final class

Replaces RuntimeCallHandler with a retry feature All scenarios or features OPT-IN to retry behaviour with the @retry tag.

Helpers for working with steps

Same principle as core TestMailer class, but saves emails in TestSessionEnvironment to share the state between PHP calls (CLI vs. browser).