Adding ability to run on-demand unit tests

[danieldeutsch]

This PR adds

• A new Github Action that will let you manually run unit tests without a push/PR
• A method to get the device ID that unit tests should be run on

This will allow us to run Docker metrics with Github Actions as necessary on the CPU. The Docker metrics would be expensive to run every time, so with this PR we could manually run the unit tests for a new Docker metric when its PR is submitted.

I am not actually sure how to test to make sure the new Action is working. I do not see it available for running on-demand on the Actions page. I don't know if this is because it has to be in the main branch first, if I don't have the required permissions, or if there's some mistake in the config. I vaguely remember not being able to see the Action until it was merged when I implemented this in Repro.

[tuetschek]

LGTM. Would looking at CUDA_AVAILABLE_DEVICES make sense for choosing the device, or does it not make sense in the context of Github?

[danieldeutsch]

We could do that, too. For the context of GitHub it does not matter since it will always use the CPU.

I'll merge this for now and we think it makes more sense to use CUDA_VISIBLE_DEVICES then I can make the change.

[danieldeutsch]

FYI It works as intended. Here are examples of running the BLEURT (https://github.com/GEM-benchmark/GEM-metrics/actions/runs/1814247777) and Prism (https://github.com/GEM-benchmark/GEM-metrics/actions/runs/1814254012) test cases with Github actions

[tuetschek]

Awesome, thanks 😊!