Fixes Particular/NServiceBus.RabbitMQ#24.
When debugger is attached, set DefaultHeartBeatInSeconds and dequeue timeout to 10 minutes.

Use connection string parameter DequeueTimeout instead of Debugger.IsAttached to set dequeue timeout in RabbitMqDequeueStrategy.

DequeueTimeout is now in seconds, and is converted to milliseconds in RabbitMqTransportFeature.Configure.