Update Composer dependencies and minimum PHP version

Upgraded various Composer package versions and updated the minimum PHP requirement to 8.1 in both `composer.json` and `composer.lock`. This includes upgrading the `composer/installers` to version 2 and modifying other dependencies to be compatible with PHP 8.1.

composer.json

@@ -10,14 +10,14 @@
     }
   ],
   "require-dev": {
-    "composer/installers": "^1.0",
+    "composer/installers": "^v2",
     "phpstan/phpstan": "^1.7",
-    "php-stubs/acf-pro-stubs": "^6.0",
+    "php-stubs/acf-pro-stubs": "^6",
     "szepeviktor/phpstan-wordpress": "^1.1",
     "phpstan/extension-installer": "^1.1",
     "yoast/phpunit-polyfills": "^1.0",
-    "php-stubs/wp-cli-stubs": "^2.10",
-    "wp-cli/wp-cli": "^2.10"
+    "php-stubs/wp-cli-stubs": "^2",
+    "wp-cli/wp-cli": "^2"
   },
   "minimum-stability": "stable",
   "prefer-stable": true,
@@ -78,6 +78,6 @@
     }
   },
   "require": {
-    "php": ">=7.4"
+    "php": ">=8.1"
   }
 }