Explicitly declare parameter types as nullable (#19)

Starting with PHP 8.4, implicit nullability triggers a deprecation warning. See https://wiki.php.net/rfc/deprecate-implicitly-nullable-types

Author: imba28

src/Codeception/Module/AMQP.php

@@ -116,7 +116,7 @@ public function _before(TestInterface $test): void
      * $I->pushToExchange('exchange.emails', new AMQPMessage('Thanks!'), 'severity');
      * ```
      */
-    public function pushToExchange(string $exchange, string|AMQPMessage $message, string $routing_key = null): void
+    public function pushToExchange(string $exchange, string|AMQPMessage $message, ?string $routing_key = null): void
     {
         $message = $message instanceof AMQPMessage
             ? $message
@@ -166,8 +166,8 @@ public function declareExchange(
         bool $auto_delete = true,
         bool $internal = false,
         bool $nowait = false,
-        array $arguments = null,
-        int $ticket = null
+        ?array $arguments = null,
+        ?int $ticket = null
     ) {
         return $this->getChannel()->exchange_declare(
             $exchange,
@@ -203,8 +203,8 @@ public function declareQueue(
         bool $exclusive = false,
         bool $auto_delete = true,
         bool $nowait = false,
-        array $arguments = null,
-        int $ticket = null
+        ?array $arguments = null,
+        ?int $ticket = null
     ): ?array {
         return $this->getChannel()->queue_declare(
             $queue,
@@ -239,8 +239,8 @@ public function bindQueueToExchange(
         string $exchange,
         string $routing_key = '',
         bool $nowait = false,
-        array $arguments = null,
-        int $ticket = null
+        ?array $arguments = null,
+        ?int $ticket = null
     ) {
         return $this->getChannel()->queue_bind(
             $queue,