CI testing of SLURM in a container environment

[benclifford]

See PR #3159 which runs Parsl tests in flux environment and (unmerged prototype) PR #3482 which does similar for kubernetes.

A couple of different groups have slurm-in-container for their own tests.

So I think the pieces are broadly there.

cc @kylechard who most recently mentioned this to me

[benclifford]

also cc @tylern4 who I have had some positive private emails with about this topic

[tylern4]

I've put some work into getting slurm working in a single container and in a docker compose setup which should help with testing. I've got a start and have the regular tests running but still need to work on the local slurm config to get tests running in the docker slurm instance.

[benclifford]

@tylern4 if you want to try that out in Parsl CI, you can make that branch a draft PR to make it happen.