Publish pfsConfig files when the PFI is light source

INSTRM-1420 lists 3 tasks that needs to be done in terms of publishing pfsDesign and pfsConfig files for different light sources.

For the upcoming November Engineering Run, please implement the last, most important task described in the above ticket, and only for pfsConfig files as standalone pfsDesign files are not needed for DRP. Namely:

When the `pfi` is the only light source, simply copy/link the pfsConfig from the fpsActor output.