[Feature Request] Support streaming responses

Use case:

As a connector developer
I want to send multiple responses for the same request
So that I can reduce the size of a single response and improve the latency for the first answer.

Todo:

* Extend CommandExecutor to support multiple responses e.g.
```csharp
public required Func, CancellationToken, Task>>> OnCommandReceived { get; set; }
```
* Extend `CommandResponseMetadata` with `ResponseMessageId` as well as `IsLastResponse` propeties
* Extend `AkriSystemProperties` with `ResponseMessageId` (proposal ReservedPrefix + "respId")
* Extend `AkriSystemProperties` with `LastResponse` (proposal ReservedPrefix + "lastResp")

Start by tracing CommandExecutor handling of OnCommandReceived, then inspect CommandResponseMetadata and AkriSystemProperties where response metadata and reserved properties are defined. Follow the existing single-response flow to determine how multiple responses are emitted and identified; done means streamed responses carry response IDs and correctly mark the final response.

Written by the indexing model from the issue text.