Update the LWTNN scripts

Summary

This MR introduces the following changes

• Cleaning up the create_lwtnn_vardict.py and the conv_lwtnn_model.py.
• Fix the error-prone check_lwtnn-model.py. A little yaml config file is now required to run the script to ensure that everything is set correctly and for reproducibility.
• An example yaml config + documentation how to run the check_lwtnn-model.py is provided.

Conformity

• Changelog entry
• Documentation
• Development guidelines
• Style guides