Add support for autodetection of gres resources

[jovial]

Adds support for setting the AutoDetection property on gres resources. This prevents the need to manually specify File in the gres dictionary. You can only use one auto-detection mechanism per node, otherwise slurm will complain - hence why it is a per-nodegroup option and not a per-gres option.

Example:

# group_vars/all/openhpc.yml

openhpc_nodegroups:
    - name: cpu
    - name: gpu
      gres_autodetect: nvml
      gres:
        - conf: "gpu:nvidia_h100_80gb_hbm3:2"
        - conf: "gpu:nvidia_h100_80gb_hbm3_4g.40gb:2"
        - conf: "gpu:nvidia_h100_80gb_hbm3_1g.10gb:6"

NB: autodetection requires rebuild of the OpenHPC packages - this is not provided by this role

[sjpb]

Have some concerns

[jovial]

Ready for review but merge #183 first (this PR targets that branch to avoid noise in diff)

[sjpb]

Few comments, but looks pretty good to me.

[sjpb]

Looks great.