`JSONImport.eval`  (and the other eval routines) should be moved under `mathics.eval`

[JSonImport.eval](https://github.com/Mathics3/mathics-core/blob/20b079da14d766af32ed971899cc48c7f6ba941a/mathics/builtin/fileformats/jsonformat.py#L35-L42) in  `mathics.builtin.fileformat.jsonformat`  (and the other importer eval routines) should be moved under `mathics.eval`

_Originally posted by @rocky in https://github.com/Mathics3/mathics-core/pull/1583#discussion_r2653908425_
            