Add ByteString ToReadOnlySpan

[fmg-lydonchandra]

Fixes #7488

Changes

Add ByteString ToReadOnlySpan, which has NO memory copy, compared to ToArray(), when ByteString is compact.

Why?

Currently we do a lot of RabbitMQ IncomingMessage Deserialization by calling ToArray() (which does memory copying)

        var evt = JsonSerializer.Deserialize<T>(message.Message.Bytes.ToArray(), SerializerOptions);

Using ToReadOnlySpan, memory copy can be avoided, as most of our IncomingMessage is compact

Checklist

For significant changes, please ensure that the following have been completed (delete if not relevant):

• This change follows the Akka.NET API Compatibility Guidelines.
• I have reviewed my own pull request.
• Design discussion issue Add ByteString ToReadOnlySpan() #7488
• Changes in public API reviewed, if any.
• I have added website documentation for this feature.

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[fmg-lydonchandra]

Hi, is this change worth having? if so, will add tests.

[Aaronontheweb]

Hi, is this change worth having? if so, will add tests.

LGTM - please add some tests

[fmg-lydonchandra]

Hi @Aaronontheweb ,PR Review please.
The unit tests are quite flaky, the .NET Multi-Node Tests fails for unrelated reason to the PR, i think.

[Aaronontheweb]

Will do

[Aaronontheweb]

LGTM

[Aaronontheweb]

Sucks that we have to allocate here but there's no way around it: Span<T> requires units to be allocated contiguously