Per-queue RabbitMQ DLX overrides ignored when transport DLX is customized

[frankvdb7]

Describe the bug
Per-queue RabbitMQ dead-letter exchange overrides are ignored. When a transport level DLX is customized and a specific queue sets its own DLX, the queue is still created with the transport default x-dead-letter-exchange.

To Reproduce

1. Configure RabbitMQ with a transport-level DLX:

     opts.UseRabbitMq().CustomizeDeadLetterQueueing(new DeadLetterQueue("default-dlq")
     {
         ExchangeName = "default-dlx-exchange"
     });

2. Configure a queue with its own DLX override:

     opts.ListenToRabbitQueue("queue-alpha")
         .DeadLetterQueueing(new DeadLetterQueue("queue-alpha-dlq")
         {
             ExchangeName = "queue-alpha-dlx-exchange"
         });

3. Start the app and inspect the declared queue arguments in RabbitMQ.
4. Observe that queue-alpha has x-dead-letter-exchange = default-dlx-exchange instead of queue-alpha-dlx-exchange.

Expected behavior
Each queue should honor its own DLX override, so queue-alpha should be declared with x-dead-letter-exchange = queue- alpha-dlx-exchange.

Screenshots
N/A

Additional context
Occurs when both a transport-level DLX and a per-queue DLX are configured; the shared DLQ instance causes the queue to pick up the transport default.