Fix bugs in JSON serialization

Found and fixed the following bugs:

Fix version checks in network_from_dict
Emit proper warning for older versions
Add missing max_loading for lines
Add missing max_loading for transformers
Add missing tap for transformers
Fix error due to sorting of line parameters and transformer parameters with heterogeneous ID types
Fix conversion of single and center transformer types to proper vector groups
Fix upgrading of max_current, conductor_type, and insulator_type of line parameters

These bugs were found with testing more comprehensive JSON files. I added files for all JSON versions and the corresponding file generator scripts.

I also added a test to ensure these files do not get modified by mistake when refactoring the code base.

RoseauTechnologies / Roseau_Load_Flow