[RM-8430] [LSF] add a source size paramater to all LSF types

Created on 2023-10-20 14:23:41 by Didier Vibert. % Done: 0

This source size parameter will be added quadratically to the sigma(lambda).

It should in the parameters.json (whatever the LSF type is, even for the "FROMSPECTRUMDATA" type) and overridden by the input spectra if available.
This solution does not give the user the ability to cancel a possibly badly estimated source size present in the spectrum. We might implement it later on, if needs be.