[Util] Introduce FileHasher

[staabm]

1:1 extracted from #3809 to make it smaller

[staabm]

guess the failling test is related to some PR merged to master, not this one?

1) Rector\Tests\Arguments\Rector\RectorOrder\RectorOrderTest::test with data set #0
Failed on fixture file "fixture.php.inc"
Failed asserting that string matches format description.
--- Expected
+++ Actual
@@ @@
 {
     public function test()
     {
-        $this->assertContains('f', 'foo');
-        $this->assertContains('f', 'foo');
+        $this->assertStringContainsString('f', 'foo');
+        $this->assertStringContainsString('f', 'foo');
 
-        $this->assertContains('oauth_body_hash', $headers['Authorization'][0]);
+        $this->assertStringContainsString('oauth_body_hash', $headers['Authorization'][0]);
     }
 }

/home/runner/work/rector-src/rector-src/packages/Testing/PHPUnit/AbstractRectorTestCase.php:178
/home/runner/work/rector-src/rector-src/packages/Testing/PHPUnit/AbstractRectorTestCase.php:131
/home/runner/work/rector-src/rector-src/rules-tests/Arguments/Rector/RectorOrder/RectorOrderTest.php:19

---

just confirmed I get this error also on the master branch

---

Update: Fixed in #3837

[samsonasik]

Thank you @staabm