minor #15614 consistently use str_replace to unify directory separators (Tobion)

This PR was merged into the 2.3 branch.

Discussion
----------

consistently use str_replace to unify directory separators

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        | -

We used a mix of `str_replace` and `strtr` for the same thing. `str_replace` is faster as [I tested myself](https://3v4l.org/MNrgC) which is logical since strtr adds logic we don't need here.

Commits
-------

b9760ef consistently use str_replace to unify directory separators

Author: fabpot

Iterator/ExcludeDirectoryFilterIterator.php

@@ -44,7 +44,7 @@ public function __construct(\Iterator $iterator, array $directories)
     public function accept()
     {
         $path = $this->isDir() ? $this->current()->getRelativePathname() : $this->current()->getRelativePath();
-        $path = strtr($path, '\\', '/');
+        $path = str_replace('\\', '/', $path);
         foreach ($this->patterns as $pattern) {
             if (preg_match($pattern, $path)) {
                 return false;

Iterator/PathFilterIterator.php

@@ -29,7 +29,7 @@ public function accept()
         $filename = $this->current()->getRelativePathname();
 
         if ('\\' === DIRECTORY_SEPARATOR) {
-            $filename = strtr($filename, '\\', '/');
+            $filename = str_replace('\\', '/', $filename);
         }
 
         // should at least not match one rule to exclude