The autoscaling GitLab CI runners currently used for most GitLab CI jobs
spin up AWS EC2 instances that are at least as powerful as the dedicated
instances used for running "stress" tests. Move all Linux-based
"stress" tests to autoscaling GitLab CI runners to enable deprovisioning
Linux AWS instances reserved for running "stress" tests. Leave FreeBSD
"stress" tests intact as there is currently no support for autoscaling
BSD instances.