Don't mutate options when calling extend

[rainhead]

Fixes: #3746.

Please try this out locally. It wasn't easy to figure out how to set up test data.

Before:

After:

In some places we're good about extending into a new object, in others we're not.

[frewsxcv]

In case you don't already know, you can do this instead without needing lodash/underscore:

$(status).css({
    ...$.fn.simpleTaxonSelector.styles.statuses['default'],
    ...$.fn.simpleTaxonSelector.styles.statuses.unmatched
})

[rainhead]

Thanks for reaching out. There's quite a lot that could be improved with modern JS here, but I'm trying to stay consistent within a code unit, and to make minimal changes. Also, the most important calls to extend here perform deep merges, which I don't think I can do with plain JS.