remove dataclasses_json (and maybe dataclasses)

[dperl-dls]

currently we have a mixture of pydantic models with some legacy dataclasses_json here and there (notably __main__.py) - we should streamline this and remove the dependency on dataclasses-json. this should basically just work as is by changing them to pydantic.dataclasses, and possibly changing some.to_json()to.json()`

maybe we can also change other basic dataclasses but that's less important as they are in the standard lib and not a dependency