lca classify and lca summarize only support JSON query signatures!

[ctb]

oops.

they should support the whole panoply of signature loading #1877

[ctb]

ref #1877

[ctb]

digging into this a little bit now, and I was somewhat mistaken.

Note that the LCA subcommands take multiple query sigs via --query so they should not use load_query_signature.

src/sourmash/lca/command_classify.py uses sourmash_args.load_file_as_signatures(...), which is pretty generic. It only supports ksize selection and could stand to be upgraded to support moltype selectors, but that's about it.

src/sourmash/lca/command_summarize.py uses MultiIndex.load_from_path, which only loads JSON files. So this could usefully be upgraded to use sourmash_args.load_file_as_signatures(...) I think.

[ctb]

note, before closing this when #2107 is merged, we should add an issue about supporting moltype selector on command line.

[ctb]

closed by #2107 and addition of #2172