Suggestion: Add a way to show version numbers of modules loaded in flux

[kkier]

flux version can tell me the versions of commands/libflux-core/libflux-security, and flux module list combined with rpm -q can mostly determine what's what, but it would be nice to have a way to get that info from flux's perspective. rpm -q tells me what's installed, but not necessarily what's running at a given time. I'm thinking about situations like the jgf changes in flux-coral2 v0.17.0 as we move forward and wanting and easy way to trap version info for diagnostics.