refactor: use slices package for sort (#10132)

The sort package is still used in places that were not trivial to
change. Since Go 1.21 slices package can be uswed for sort. See
https://go.dev/doc/go1.21#slices

### Purpose

Make some progress with the migration to a more up-to-date syntax.

lib/fs/basicfs_xattr_bsdish.go

@@ -12,7 +12,7 @@ package fs
 import (
 	"errors"
 	"fmt"
-	"sort"
+	"slices"
 	"unsafe"
 
 	"golang.org/x/sys/unix"
@@ -69,7 +69,7 @@ func listXattr(path string) ([]string, error) {
 		}
 	}
 
-	sort.Strings(attrs)
+	slices.Sort(attrs)
 	return attrs, nil
 }