Add chain_iptm

[samuelmurail]

Hi

Following @milot-mirdita suggestion I am doing the pull request on the right deposit.

#sokrypton#3 (comment)

I struggled to extract the chain_num from asym_id tracer, that seemed trivial, but with the jax library (first experience for me), it was impossible for me. So I add to extract it from c.embeddings_and_evoformer.max_relative_chain.

chain_iptm and the whole ptm_matrix are added to the confidence_metric dictionnary.

Concerning the whole ptm_matrix I think it should be saved as the pae matrix, to later be treated and for example extract the interface iptm as in af2complex.

I will also do a pull request on colabfold to save the chain_iptm and ptm_matrix is the json output.

Cheers,
Samuel