update charcoal with functions from `sourmash.tax`

[ctb]

With the merge of https://github.com/sourmash-bio/sourmash/pull/1543 and https://github.com/sourmash-bio/sourmash/pull/1651, among others, we have a lot of ~duplicated functionality between charcoal and sourmash. We should change charcoal over to using sourmash functions where possible, just as we did with sourmash.lca.lca_utils stuff in https://github.com/dib-lab/charcoal/pull/203.