Add test showing current behaviour when testsuite is missing name attribute in XML configuration

Author: kubawerlos

tests/_files/configuration.testsuite_no_name.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit>
+    <testsuite>
+        <directory>tests</directory>
+    </testsuite>
+</phpunit>

tests/end-to-end/generic/defaulttestsuite-using-testsuite-without-name.phpt

@@ -0,0 +1,15 @@
+--TEST--
+phpunit --configuration=__DIR__.'/../../_files/configuration.testsuite_no_name.xml'
+--FILE--
+<?php declare(strict_types=1);
+$_SERVER['argv'][] = '--do-not-cache-result';
+$_SERVER['argv'][] = '--no-progress';
+$_SERVER['argv'][] = '--configuration';
+$_SERVER['argv'][] = __DIR__.'/../../_files/configuration.testsuite_no_name.xml';
+
+require_once __DIR__ . '/../../bootstrap.php';
+(new PHPUnit\TextUI\Application)->run($_SERVER['argv']);
+--EXPECTF--
+PHPUnit %s by Sebastian Bergmann and contributors.
+
+assert(!empty($name))