Rename taxonomy kinds from taxonomy to term, taxonomyTerm to taxonomy

And we have taken great measures to limit potential site breakage:

* For `disableKinds` and `outputs` we try to map from old to new values if possible, if not we print an ERROR that can be toggled off if not relevant.
* The layout lookup is mostly compatible with more options for the new `term` kind.

That leaves:

* Where queries in site.Pages using taxonomy/taxonomyTerm Kind values as filter.
* Other places where these kind value are used in the templates (classes etc.)

Fixes #6911
Fixes #7395

hugolib/content_map_page.go

@@ -106,7 +106,7 @@ func (m *pageMap) newPageFromContentNode(n *contentNode, parentBucket *pagesMapB
 	sections := s.sectionsFromFile(f)
 
 	kind := s.kindFromFileInfoOrSections(f, sections)
-	if kind == page.KindTaxonomy {
+	if kind == page.KindTerm {
 		s.PathSpec.MakePathsSanitized(sections)
 	}
 
@@ -535,7 +535,7 @@ func (m *pageMap) assembleTaxonomies() error {
 			}
 		} else {
 			title := ""
-			if kind == page.KindTaxonomy {
+			if kind == page.KindTerm {
 				title = n.viewInfo.term()
 			}
 			n.p = m.s.newPage(n, parent.p.bucket, kind, title, sections...)