Create an --all_structs flag for populate_modelcif.py, capture *every* model & seed

[keiran-rowell-unsw]

Was discussed in the SBF facility meeting. Since the pipeline already emits the best predicted structure in top_ranked_structures by default, it that separateness of "rank_0" as the "best" predicted structure should be preserved.

However, it is also helpful to have a single .mmcif files to share with colleagues that has all atomic data of the Assembly without having to re-spec everything about the model run in separate files.

This is provided by .model.Model

Since I learnt how to implement flags with --write_binary to implement #583, should also include a --all_structs with default presence boolean False (action='store_true' in argparse)

EDIT: implemented with fixed rank_{0..4} rather than a glob because nextflow shell parsing was causing issues. Will validate in real-pipeline that structure globbing is being passed (and rejected) properly by:

    if all_structs:
        for struct_file in struct_files:
            try:
                biopy_struct = _parse_structure(struct_file)
            except Exception as err:
                print(
                    f"Skipping unparseable structure file {struct_file}: {err}",
                    file=sys.stderr,
                )
                continue
            selected_struct_files.append(struct_file)
            biopy_structs.append(biopy_struct)