Petals CDK

The acceptor thread pool is a fixed size list of threads. Each thread accepts messages from the delivery channel before to give them to the message processors.

In relation with PETALSCDK-135, the goal is to rewrite the Acceptor/Processor message handling.

The final result should be something like this:

• Acceptor threads that dies are recreated
• There is only one acceptor thread by default (there should be no need for more, but who knows... so we keep the pool)
• There is a pool for the processor threads (and we remove the pool of processors) (and the CDK parameter message-processor-max-pool-size is removed)
• Acceptor that are waiting in retry stop waiting as soon as a new processor is available