dlq_purge: Show what queues messages came from

[ndevenish]

Now shows which queues messages came from, instead of mixing together outputs in somewhat arbitrary order. New output:

Looking for DLQ messages in 38 queues...
Found 13 DLQ messages in dlq.ispyb_connector
    Message 1 (2025-06-16 13:27:41) exported:
        /dls/tmp/zocalo/DLQ/2025-06-16/msg-20250616-132741-000-1
    Message 2 (2025-06-16 13:27:41) exported:
        /dls/tmp/zocalo/DLQ/2025-06-16/msg-20250616-132741-000-2
    Message 3 (2025-06-16 13:27:41) exported:
        /dls/tmp/zocalo/DLQ/2025-06-16/msg-20250616-132741-000-3
    Message 4 (2025-06-16 13:27:41) exported:
        /dls/tmp/zocalo/DLQ/2025-06-16/msg-20250616-132741-000-4
Done.

Also, accepts dlq.* names in rabbitmq, stripping off the dlq. part if present.

[ndevenish]

Tested with multiple queues

Looking for DLQ messages in 38 queues...
Found 2 DLQ messages in dlq.cloudwatcher
    Message 1 (2025-06-17 10:35:25) exported:
        /dls/tmp/zocalo/DLQ/2025-06-17/msg-20250617-103525-000-1
    Message 2 (2025-06-17 10:35:32) exported:
        /dls/tmp/zocalo/DLQ/2025-06-17/msg-20250617-103532-000-2
Found 1 DLQ messages in dlq.cluster.submission
    Message 1 (2025-06-17 10:43:16) exported:
        /dls/tmp/zocalo/DLQ/2025-06-17/msg-20250617-104316-000-1
Found 330 DLQ messages in dlq.per_image_analysis
    Message 1 (2025-06-16 19:21:53) exported:
        /dls/tmp/zocalo/DLQ/2025-06-16/msg-20250616-192153-000-1
    Message 2 (2025-06-16 19:21:53) exported:
        /dls/tmp/zocalo/DLQ/2025-06-16/msg-20250616-192153-000-2
    Message 3 (2025-06-16 19:21:53) exported:
        /dls/tmp/zocalo/DLQ/2025-06-16/msg-20250616-192153-000-3
    Message 4 (2025-06-16 19:21:53) exported:
        /dls/tmp/zocalo/DLQ/2025-06-16/msg-20250616-192153-000-4
    Message 5 (2025-06-16 19:21:53) exported:
        /dls/tmp/zocalo/DLQ/2025-06-16/msg-20250616-192153-000-5
...
    Message 330 (2025-06-16 19:21:56) exported:
        /dls/tmp/zocalo/DLQ/2025-06-16/msg-20250616-192156-000-330
Done.