publisher: Exclude comment and doctype elements from writeStats

- Reorder code blocks
- Rename cssClassCollectorWriter to htmlElementCollectorWriter, as it just collect html element information
- Expand benchmark to test for minified and unminified content

Fixes #8396
Fixes #8417

hugolib/site_test.go

@@ -1113,7 +1113,7 @@ ABC.
 		els := stats.HTMLElements
 
 		b.Assert(els.Classes, qt.HasLen, 3606) // (4 * 900) + 4 +2
-		b.Assert(els.Tags, qt.HasLen, 9)
+		b.Assert(els.Tags, qt.HasLen, 8)
 		b.Assert(els.IDs, qt.HasLen, 1)
 	}
 }