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/resource_chain_test.go

@@ -895,7 +895,7 @@ h1 {
 
 	newTestBuilder := func(v *viper.Viper) *sitesBuilder {
 		v.Set("workingDir", workDir)
-		v.Set("disableKinds", []string{"taxonomyTerm", "taxonomy", "page"})
+		v.Set("disableKinds", []string{"taxonomy", "term", "page"})
 		b := newTestSitesBuilder(t).WithLogger(loggers.NewWarningLogger())
 		// Need to use OS fs for this.
 		b.Fs = hugofs.NewDefault(v)