Make "Scheduling GPUs" its own (sub-)section

[SteVwonder]

This should include details about hwloc needing to be compiled against NVML and OpenCL. The check for if GPU detection in Flux worked (#71). And that CUDA_DEVICE_ORDER should be set if launching with a system launcher like srun or jsrun.

[SteVwonder]

Instructions for loading GPU-enabled Flux on TOSS systems:

module use /opt/modules/modulefiles
module use /usr/global/tools/flux/toss_3_x86_64_ib/modulefiles
module load flux/0.19.0-cuda

Confirm that Flux is detecting GPUs and marking them as schedulable:

❯ flux start flux resource list                                                                                                                                                                                                13:24:14 ()
     STATE NNODES   NCORES    NGPUS
      free      1       16        2
 allocated      0        0        0
      down      0        0        0

[SteVwonder]

It should also cover the fact that if you don't have Fluxion loaded, hwloc may be detecting and reporting GPUs but sched-simple is ignoring them.

To test if hwloc is detecting them: flux start flux hwloc topology | grep CoProc. To test that fluxion is loaded: flux module list | grep fluxion (you should see a qmanager and resource module). If all of that is together, then flux resource list should list the GPUs.