Make sequence field optional in odgi bin when output via --json

[subwaystation]

No description provided.

[josiahseaman]

Code added on component_segmentation should match header variable names:

            if "odgi_version" in path:
                # this is the header
                assert path["odgi_version"] == ODGI_VERSION, f"Expecting version {ODGI_VERSION}." \
                    f"This version added the header with pangenome nucleotide count."
                print(f"Found file with {path['pangenome_length']} nucleotides in the pangenome and"
                      f" a bin size of {path['bin_width']}bp Bin width.")

I'm starting with ODGI_VERSION 10. But these numbers will likely diverge since not every update in one requires and update in the other.