Accelerator support

[rivershah]

Feature request to expose gpu support for ci_workers. For unit testing am requiring GPUs. Use case is verification and testing of machine learning code and cpu only machines is not an option as behaviour changes sufficiently to require testing on target devices. It is not immediately obvious how gpu accelerators can be used with ci_workers. The required machine configs for the ci_workers are:

machine_type = "n1-standard-8"
guest_accelerator {
  type  = "nvidia-tesla-t4"
  count = 2
}

machine_type = "a2-highgpu-4g"
guest_accelerator {
  type  = "nvidia-tesla-a100"
  count = 4
}

Sorry I don't have the skill set to fully understand how the machine image, nvidia driver loading and any cuda dependencies need to work with the gitlab runner or would have submitted a PR