Reduce memory usage

[SoftStoneDevelop]

Usage:

var producerConfig = new DeduplicatingProducerConfig(...)
{
    ConfirmationHandler = async confirmation =>
    {
        // call dispose on each confirmation.Messages or do nothing
    },
};

var producer = await DeduplicatingProducer.Create(producerConfig, ...);
// start producer...

// send new message
var memory = MemoryPool<byte>.Shared.Rent(10);
// fill memory...

await producer.Send(
    messageId,
    new Message(memory, 10));

[Gsantomaggio]

Thank you for your PR. I will check it as soon as possible

[Gsantomaggio]

@SoftStoneDevelop, may I ask for a report on the memory gain? We'd like to see some numbers. We will change the Message class, which is critical for the library and we have to be sure.
Thank you.

[lukebakken]

This is the sort of change that requires more planning. It makes sense to add *Memory-specific APIs to the project, but I'm not thrilled with how it becomes this library's responsibility for managing the lifetime of the externally-rented memory.

@SoftStoneDevelop - when you open a pull request, the best practice is to do so from a change-specific branch on your fork. Since you have opened a PR from main, I can't push changes to your fork.

I'm going to close this PR and start a discussion for version 2.0.