Most MediaWiki repositories now have a composer test. The PHPUnit tests already install the composer dev dependencies and thus we should be able to run composer test directly in the job that runs the PHPUnit tests.
- we stop triggering the composer tests extra jobs that consume instances
- if lint/style fails, the PHPUnit jobs are not run at all and feedback is given faster
Since some MediaWiki repositories might lack a composer.json or a test entry point, we would have to take that in account.