path/filepath: add Localize

Implemented filepath.Localize using internal/safefilepath.FromFS.

Fixes golang#57151

Change-Id: I98c6a211d77fa5c8733306b5ef39950bae07fb5c

api/next/57151.txt

@@ -0,0 +1 @@
+pkg path/filepath, func Localize(string) (string, error) #57151

src/path/filepath/path.go

@@ -13,6 +13,7 @@ package filepath
 
 import (
 	"errors"
+	"internal/safefilepath"
 	"io/fs"
 	"os"
 	"runtime"
@@ -681,3 +682,12 @@ func Dir(path string) string {
 func VolumeName(path string) string {
 	return FromSlash(path[:volumeNameLen(path)])
 }
+
+// Localize converts a slash-separated path into an operating-system path.
+//
+// Localize returns an error if the path cannot be represented by the operating
+// system. For example, paths containing '\' and ':' characters are rejected
+// on Windows.
+func Localize(path string) (string, error) {
+	return safefilepath.FromFS(path)
+}