Introduce read only-path for tables?

[Jean1995]

At the moment, there is only one PROPOSAL::InterpolationSettings::TABLES_PATH. PROPOSAL will read interpolation tables from there, if required. But if they are not found, PROPOSAL will also write tables to there.

This might not be desired in some cases. I believe IceCube had a problem with this, and CORSIKA 8 containers might also have a problem with this.

In PROPOSAL 6 we had something like tables_read_only paths, where it was clear that PROPOSAL should only read tables from there, but never write to these paths. Maybe this would also be useful? Or we introduce something like a list of TABLE_PATHS, and every PATH has a setting whether it is read-only or not.

[MaxSac]

Why does the process have the right to write to the folder if it is not supposed to?