Draft proposal for "Laguna Gold" - Lightweight SDKs

[davidmrdavid]

Just checkpointing my hackathon prototype. Given the changes in the DF layer (Azure/azure-functions-durable-extension#1963), an OOProc SDK now has a lot less work to do. In short, we can safely remove most of the TaskOrchestrationExecutor and replace it with about ~50 lines of code with simple logic.

Essentially, we run the user code until a task is yielded. That task is then looked-up in the extension's "tasks" payload and, if found, the task in the SDK is assigned a value and the replay continues. If not found, we can return. Super simple :-)

The most important takeaway is that having the task state communicate by the extension removes the need to have so much DF domain knowledge in order to implement and maintain a DF SDK.

This is by no means "clean code" nor an optimal way to implement this. I'm mostly creating this PR for communication and visibility purposes.