Demonstrate first-class PHP configuration (Codeception PR #6946)

Replace the YAML Codeception config with the new PHP config format and
link codeception/codeception to the php_config branch (PR #6946) so the
GlobalConfig / SuiteConfig builders are available.

- Delete codeception.yml and tests/Functional.suite.yml
- Add codeception.php and tests/Functional.suite.php (equivalent config)
- composer: add a VCS repo for Codeception/Codeception and require
  "dev-php_config as 5.3.x-dev"; refresh composer.lock accordingly
- CI: also trigger on the 8.1-php-config branch

Illustrative / draft only: do not merge until PR #6946 lands, after which
the composer link must revert to a stable codeception/codeception release.

Verified: config:validate loads the .php config, and the Functional suite
passes (138 tests, 258 assertions) against the php_config core.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: TavoNiievez

.github/workflows/symfony.yml

@@ -4,9 +4,11 @@ on:
   push:
     branches:
       - '8.1'
+      - '8.1-php-config'
   pull_request:
     branches:
       - '8.1'
+      - '8.1-php-config'
 
 env:
   APP_ENV: test

codeception.php

@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+use Codeception\Config\GlobalConfig;
+use Codeception\Extension\RunFailed;
+
+return GlobalConfig::create()
+    ->namespace('App\Tests')
+    ->supportNamespace('Support')
+    ->paths(
+        tests: 'tests',
+        output: 'tests/_output',
+        data: 'tests/Support/Data',
+        support: 'tests/Support',
+        envs: 'tests/_envs',
+    )
+    ->actorSuffix('Tester')
+    ->extension(RunFailed::class)
+    ->params('.env', '.env.test')
+    ->settings(shuffle: true, colors: true, reportUselessTests: true);

codeception.yml

@@ -3,6 +3,12 @@
     "description": "Codeception Symfony Module tests",
     "type": "project",
     "license": "MIT",
+    "repositories": [
+        {
+            "type": "vcs",
+            "url": "https://github.com/Codeception/Codeception.git"
+        }
+    ],
     "authors": [
         {
             "name": "Gustavo Nieves",
@@ -31,7 +37,7 @@
         "symfony/yaml": "8.1.*"
     },
     "require-dev": {
-        "codeception/codeception": "^5.3",
+        "codeception/codeception": "dev-php_config as 5.3.x-dev",
         "codeception/module-asserts": "^3.2",
         "codeception/module-doctrine": "^3.3",
         "codeception/module-symfony": "^3.8 | *@dev",