Add ability to read layer_map for pytorch model bin files

[charlesmartin14]

Some open source models like Mistral-7b have 2 pytorch_model.bin files, BUT the order of the layers is changed
i.e

https://huggingface.co/mistralai/Mistral-7B-Instruct-v0.1/

The order of the layers is given in

pytorch_model.bin.index.json

Weightwatcher needs some way to fix the ordering of the layers

say after running analyze() by reading the final map file and fixing the ordering

This approach could be used for safetensors also

Note that if the order is not sequential, we can not run intra=True, but thats ok for now