Prevent external name provider from attempting imports into locked taxa

It is frequently the case that people use the external name provider to bring in names that belong under locked taxa (mammals, birds, etc.). These end up ungrafted and often require significant curation effort. It would be really helpful for curators if we could ask the external name provider for ancestors of potential imports and prevent names that are descendants of iNat locked taxa. I think a best case scenario would give an error message directing people to instead use flags.

Brief discussion here: https://forum.inaturalist.org/t/locked-taxa-and-search-external-name-providers/10147

Related request here: https://forum.inaturalist.org/t/search-both-tfr-synonyms-and-unaccepted-scientific-names-for-taxon-matches/13843

I support this. If I’m importing taxa to a list then I do tend to search external name providers. This can sometimes give suggestions for synonyms which makes the function useful even for locked taxa. However it can also lead to the taxon being imported (which can often be desirable in the case of unlocked taxa but not locked taxa). I certainly don’t want to add to the workload of curators unnecessarily.