IngestPfsImages should not create a PfsConfig by default if none exists

ingestPfsImages.py ingests raw exposures to the specified raw data repository, and the corresponding pfsConfig file for that exposure.

If the pfsConfig file does not exist, then by default it creates one from the appropriate pfsDesign file (which is found from the value of the pfsDesignId in the raw exposure header):

https://github.com/Subaru-PFS/obs_pfs/blob/52849390d4fce2815f976c9ce1e6df5da24abff4/python/lsst/obs/pfs/ingest.py#L551-L558

During normal operations, the pfsConfig will be created by the ICS software. So the non-existence of a pfsConfig file for that exposure should be raised immediately as an error.

As the facility of creating a pfsConfig if one does not exist is useful for development purposes and commissioning it should be retained.

So instead please update the code such that the creation of a pfsConfig file if one does not exist is provided as a configuration parameter, which by default is off.