Explicit code generation in datamodel glue might be replaceable with variadic template function

[tmadlener]

This is somewhat of a drive-by comment that I just discovered while checking something unrelated entirely.

Since AIDASoft/podio#761 (aka podio >= 1.3) it should in principle be possible to replace the python based code generation that implements the visitor pattern for podio generated datamodels (https://github.com/eic/EICrecon/blob/main/src/services/io/podio/make_datamodel_glue.py) with a variadic template based visitor that simply walks all types in EDM4hep and EMD4eic.

We have used this in some cases in EDM4hep already to cut down on having to hard-code type names (or generate them with an external process). See, e.g. key4hep/EDM4hep#443

I think something similar should be possible here, but I was not sure whether the required bump in minimal podio version is something that you would be willing to consider.