Draft: allow specifying custom pre-run scripts on host and container side

This is a more generic way of achieving what !4 is doing by allowing the configuration inject a custom script either into the host side (for triggering the CUDA driver load) or on the device side (for modifying environment variables to deal with issues I've been having with the defaults for apptainer ROCm binds)

I'm not familiar with the test framework yet, so I marked this as a draft until I know how to test it.