[Feature]: support async functions

[zhongkechen]

What would you like?

I would like my durable handler and steps to be async

@async_durable_step
async def my_step(step_context, data):
    # Your business logic
    return result

@async_durable_execution
async def handler(event, context: AsyncDurableContext):
    result = await context.step(my_step(event["data"]))
    return result

Possible Implementation

No response

Is this a breaking change?

No

Does this require an RFC?

No

Additional Context

No response