Add variables to configure allow_failure in all linting jobs
Problem/Motivation
If a you've got all the linting jobs green on your project it'd be nice to make it easy to set allow_failure to FALSE on all of them otherwise pipelines look green when you'd consider them a fail.
This is compounded by the fact that drupal.org visually adds a green tick pipelines where there is a warning (which is another probably more important bug).
Steps to reproduce
Have a pipeline that gets PHPStan warnings... see green in the drupal.org issue.
Proposed resolution
Make it simple for projects to set allow_failures to FALSE with variables.