Add a working comparative GPU benchmark workflow/action

[samuelburnham]

There is enough common ground between https://github.com/lurk-lab/lurk-rs/blob/main/.github/workflows/merge-tests.yml#L69 and lurk-lang/arecibo#238 that we should be able to factor out some if not all steps into a reusable workflow or action.

This will help us extend GPU benchmarks to other performance-centric repos in the future like https://github.com/lurk-lab/grumpkin-msm