Implement Transaction and Rollback for fixtures

[rossmitchell]

Before running fixtures

foreach ($fixturesToLoad as $fixture) {
            if (!$fixture instanceof FixtureInterface) {
                $fixture = $fixturesHelper->createFixture($fixture);
            }
            $fixturesHelper->addFixture($fixture);
        }
        $this->connection->getConnection()->beginTransaction();
        $this->fixturesHaveBeenRun = true;
        $fixturesHelper->setCacheKey(static::class);
        $fixturesHelper->run();`

In tearDown Method

$this->connection->getConnection()->rollBack();