Conversion of JGF version and grow support

[vsoch]

Fluxion currently requires JGF version 1. The version 2 is a better design that allows for indexing the nodes based on name (as opposed to a list) and there are subtle differences in the design. I would prefer to continue developing tools (e.g., compspec-go) anticipating v2, so I think an OK strategy for the time being will be to allow fluence to accept a v2 and convert to v1 to give to flux. I'll be able to implement this shortly when I'm ready (I'm currently adding the export of the cluster graph from compspec-go, which I'm going to use version 2 for). This will mean that:

• compspec-go extracts node-level metadata comspec extract
• the nodelevel metadata is assembled into JGF v2 compspec create nodes
• the nodes (v2) are sent to the rainbow scheduler, which TBA will have some variant of fluxion (I hope) that can accept the v2 and convert to v1 before sending to the underlying library via the bindings.

[vsoch]

I realize we will need not just an ability to convert JGF for rainbow, but also the grow functionality in flux-sched. I think @zekemorton is working on the guts of that? And I think a part of it might be here? flux-framework/flux-sched#1061

In the meantime I'll prototype a faux fluxion that can accept (and merge) different resource graphs to do some very questionable, and janky scheduling. 😆