Fix(testing): Register shutdown handler to delete temp input file

- Register shutdown function to delete the temporary input file via FileSystem::delete
- Avoid leftover test artifacts by removing fixture-derived files on process exit
- Return $inputFilePath and ensure it is cleaned up after tests

Author: guanguans

src/Testing/PHPUnit/AbstractRectorTestCase.php

@@ -159,6 +159,7 @@ protected function doTestFile(string $fixtureFilePath, bool $includeFixtureDirec
 
         // write temp file
         FileSystem::write($inputFilePath, $inputFileContents, null);
+        register_shutdown_function([FileSystem::class, 'delete'], $inputFilePath);
 
         $this->doTestFileMatchesExpectedContent(
             $inputFilePath,