Ensure build tests run with restricted time out

Ok. composer-stager calls set_time_limit() so we can't start the build test server with this function disabled. But if we want to test running cron like a host that tries to limit request times set_time_limit() might be disabled. Presumably that is why drupal core provides a wrapper in \Drupal\Component\Utility\Environment::setTimeLimit()

So probably will need to file an issue with composer-stager.

Created a composer-stager issue https://github.com/php-tuf/composer-stager/issues/253

Ok. Simplified this MR now all build tests have `max_execution_time` of 10. It could be lower but it seems good to leave it higher for random drupalci slowness and to make sure it passes on local setups on slower computers.

This is nice and simple. I have no complaints!

Automatically closed - issue fixed for 2 weeks with no activity.