Split out the puthe path/filepath functions into common/paths

So they can be used from the config package without cyclic troubles.

Updates #8654

hugolib/pagecollections.go

@@ -20,6 +20,8 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/gohugoio/hugo/common/paths"
+
 	"github.com/gohugoio/hugo/hugofs/files"
 
 	"github.com/gohugoio/hugo/helpers"
@@ -187,7 +189,7 @@ func (c *PageCollections) getSectionOrPage(ref string) (*contentNode, string) {
 	langSuffix := "." + m.s.Lang()
 
 	// Trim both extension and any language code.
-	name := helpers.PathNoExt(filename)
+	name := paths.PathNoExt(filename)
 	name = strings.TrimSuffix(name, langSuffix)
 
 	// These are reserved bundle names and will always be stored by their owning