Webhook worker cancellation behavior

[steebchen]

see hatchet-dev/hatchet-typescript#106 (review) for details

from @grutt

with the current implementation, we'll make a new request to the worker to cancel the running step. with our grpc model, we send that request to the correct worker which has a ref to the running step run to cancel.
with the webhook worker, the request might get pickedup by a different lambda which will have no reference to the run...

Also, once the behavior is decided, this needs to be adapted in all SDKs individually