Removed support for Laravel 8 and therefore for PHP < 8.0 (#1504)

* Removed support for Laravel 8 and therefore for PHP < 8.0

* Update php-cs-fixer to v3

* composer fix-style

.php-cs-fixer.tests.php

@@ -0,0 +1,22 @@
+<?php
+require __DIR__ . '/vendor/autoload.php';
+
+$finder = PhpCsFixer\Finder::create()
+    ->in(__DIR__ . '/tests')
+    ->exclude('__snapshots__');
+
+$config = require __DIR__ . '/.php-cs-fixer.common.php';
+
+// Additional rules for tests
+$config = array_merge(
+    $config,
+    [
+        'declare_strict_types' => true,
+    ]
+);
+
+return (new PhpCsFixer\Config())
+    ->setFinder($finder)
+    ->setRules($config)
+    ->setRiskyAllowed(true)
+    ->setCacheFile(__DIR__ . '/.php-cs-fixer.tests.cache');